diff --git a/src/Objects/CollectionsService.php b/src/Objects/CollectionsService.php
index db7bd2b..1832293 100644
--- a/src/Objects/CollectionsService.php
+++ b/src/Objects/CollectionsService.php
@@ -87,9 +87,18 @@ class CollectionsService
                                              ActivityPubObject $collection,
                                              Closure $filterFunc )
     {
+        $sort = 'desc';
+        if ( $request->query->has( 'sort' ) && $request->query->get( 'sort' ) == 'asc' ) {
+            $sort = 'asc';
+        }
         if ( $request->query->has( 'offset' ) ) {
             return $this->getCollectionPage(
-                $collection, $request, intval( $request->query->get( 'offset' ) ), $this->pageSize, $filterFunc
+                $collection,
+                $request,
+                intval( $request->query->get( 'offset' ) ),
+                $this->pageSize,
+                $filterFunc,
+                $sort
             );
         }
         $colArr = array();
@@ -103,7 +112,7 @@ class CollectionsService
             }
         }
         $firstPage = $this->getCollectionPage(
-            $collection, $request, 0, $this->pageSize, $filterFunc
+            $collection, $request, 0, $this->pageSize, $filterFunc, $sort
         );
         $colArr['first'] = $firstPage;
         return $colArr;
@@ -113,8 +122,10 @@ class CollectionsService
                                         Request $request,
                                         $offset,
                                         $pageSize,
-                                        Closure $filterFunc )
+                                        Closure $filterFunc,
+                                        $sort )
     {
+        $asc = $sort == 'asc';
         $itemsKey = 'items';
         $pageType = 'CollectionPage';
         $isOrdered = $this->isOrdered( $collection );
@@ -129,7 +140,11 @@ class CollectionsService
         }
         $collectionItems = $collection->getFieldValue( $itemsKey );
         $pageItems = array();
-        $idx = $offset;
+        if ( $asc ) {
+            $idx = $offset;
+        } else {
+            $idx = $this->getCollectionSize( $collection ) - $offset - 1;
+        }
         $count = 0;
         while ( $count < $pageSize ) {
             $item = $collectionItems->getFieldValue( $idx );
@@ -143,22 +158,29 @@ class CollectionsService
                 $pageItems[] = $item->asArray( 1 );
                 $count++;
             }
-            $idx++;
+            if ( $asc ) {
+                $idx++;
+            } else {
+                $idx--;
+            }
         }
         if ( $count === 0 ) {
             throw new NotFoundHttpException();
         }
         $page = array(
             '@context' => $this->contextProvider->getContext(),
-            'id' => $collection['id'] . "?offset=$offset",
+            'id' => $collection['id'] . "?offset=$offset&sort=$sort",
             'type' => $pageType,
             $itemsKey => $pageItems,
             'partOf' => $collection['id'],
         );
         // TODO set 'first' and 'last' on the page
-        $nextIdx = $this->hasNextItem( $request, $collectionItems, $idx );
-        if ( $nextIdx ) {
-            $page['next'] = $collection['id'] . "?offset=$nextIdx";
+        $nextIdx = $this->hasNextItem( $request, $collectionItems, $idx, $sort );
+        if ( is_numeric( $nextIdx ) ) {
+            if ( ! $asc ) {
+                $nextIdx = $this->getCollectionSize( $collection ) - $nextIdx - 1;
+            }
+            $page['next'] = $collection['id'] . "?offset=$nextIdx&sort=$sort";
         }
         if ( $isOrdered ) {
             $page['startIndex'] = $offset;
@@ -179,15 +201,20 @@ class CollectionsService
         }
     }
 
-    private function hasNextItem( Request $request, ActivityPubObject $collectionItems, $idx )
+    private function hasNextItem( Request $request, ActivityPubObject $collectionItems, $idx, $sort )
     {
+        $asc = $sort == 'asc';
         $next = $collectionItems->getFieldValue( $idx );
         while ( $next ) {
             if ( is_string( $next ) ||
                 $this->authService->isAuthorized( $request, $next ) ) {
                 return $idx;
             }
-            $idx++;
+            if ( $asc ) {
+                $idx++;
+            } else {
+                $idx--;
+            }
             $next = $collectionItems->getFieldValue( $idx );
         }
         return false;
@@ -383,5 +410,31 @@ class CollectionsService
         $this->entityManager->persist( $collection );
         $this->entityManager->flush();
     }
+
+    public function getCollectionSize( ActivityPubObject &$collection )
+    {
+        if ( $collection->hasField( 'totalItems' ) && is_numeric( $collection['totalItems'] ) ) {
+            return intval( $collection['totalItems'] );
+        } else {
+            $itemsField = 'items';
+            if ( $collection->hasField( 'type' ) && $collection['type'] == 'OrderedCollection' ) {
+                $itemsField = 'orderedItems';
+            }
+            if ( ! ( $collection->hasField( $itemsField ) && $collection[$itemsField] instanceof ActivityPubObject ) ) {
+                return 0;
+            }
+            $items = $collection[$itemsField];
+            $count = 0;
+            $idx = 0;
+            $currentItem = $items[$idx];
+            while ( $currentItem ) {
+                $count++;
+                $idx++;
+                $currentItem = $items[$idx];
+            }
+            $collection = $this->objectsService->update( $collection['id'], array( 'totalItems' => strval( $count ) ) );
+            return $count;
+        }
+    }
 }
 
diff --git a/test/Controllers/GetControllerTest.php b/test/Controllers/GetControllerTest.php
index f3386aa..842f89c 100644
--- a/test/Controllers/GetControllerTest.php
+++ b/test/Controllers/GetControllerTest.php
@@ -42,6 +42,14 @@ class GetControllerTest extends APTestCase
                 return null;
             } )
         );
+        $objectsService->method( 'update' )->will(
+            $this->returnCallback( function ( $uri ) {
+                if ( array_key_exists( $uri, $this->objects ) ) {
+                    return $this->objects[$uri];
+                }
+                return null;
+            } )
+        );
         $authService = new AuthService();
         $contextProvider = new ContextProvider();
         $httpClient = $this->getMock( Client::class );
@@ -235,7 +243,7 @@ class GetControllerTest extends APTestCase
                             'https://www.w3.org/ns/activitystreams',
                             'https://w3id.org/security/v1',
                         ),
-                        'id' => 'https://example.com/actors/1/inbox?offset=0',
+                        'id' => 'https://example.com/actors/1/inbox?offset=0&sort=desc',
                         'type' => 'OrderedCollectionPage',
                         'orderedItems' => array(
                             array(
diff --git a/test/Objects/CollectionsServiceTest.php b/test/Objects/CollectionsServiceTest.php
index a5c8dca..0da494a 100644
--- a/test/Objects/CollectionsServiceTest.php
+++ b/test/Objects/CollectionsServiceTest.php
@@ -95,19 +95,19 @@ class CollectionsServiceTest extends APTestCase
                             'https://www.w3.org/ns/activitystreams',
                             'https://w3id.org/security/v1',
                         ),
-                        'id' => 'https://example.com/objects/1?offset=0',
+                        'id' => 'https://example.com/objects/1?offset=0&sort=desc',
                         'type' => 'OrderedCollectionPage',
                         'partOf' => 'https://example.com/objects/1',
                         'startIndex' => 0,
                         'orderedItems' => array(
                             array(
-                                'id' => 'https://example.com/objects/2',
+                                'id' => 'https://example.com/objects/4',
                             ),
                             array(
                                 'id' => 'https://example.com/objects/3',
                             ),
                             array(
-                                'id' => 'https://example.com/objects/4',
+                                'id' => 'https://example.com/objects/2',
                             ),
                         ),
                     ),
@@ -156,23 +156,23 @@ class CollectionsServiceTest extends APTestCase
                             'https://www.w3.org/ns/activitystreams',
                             'https://w3id.org/security/v1',
                         ),
-                        'id' => 'https://example.com/objects/1?offset=0',
+                        'id' => 'https://example.com/objects/1?offset=0&sort=desc',
                         'type' => 'OrderedCollectionPage',
                         'partOf' => 'https://example.com/objects/1',
                         'startIndex' => 0,
-                        'next' => 'https://example.com/objects/1?offset=4',
+                        'next' => 'https://example.com/objects/1?offset=4&sort=desc',
                         'orderedItems' => array(
                             array(
-                                'id' => 'https://example.com/objects/2',
+                                'id' => 'https://example.com/objects/6',
                             ),
                             array(
-                                'id' => 'https://example.com/objects/3',
+                                'id' => 'https://example.com/objects/5',
                             ),
                             array(
                                 'id' => 'https://example.com/objects/4',
                             ),
                             array(
-                                'id' => 'https://example.com/objects/5',
+                                'id' => 'https://example.com/objects/3',
                             ),
                         ),
                     ),
@@ -214,46 +214,19 @@ class CollectionsServiceTest extends APTestCase
                         'https://www.w3.org/ns/activitystreams',
                         'https://w3id.org/security/v1',
                     ),
-                    'id' => 'https://example.com/objects/1?offset=3',
+                    'id' => 'https://example.com/objects/1?offset=3&sort=desc',
                     'type' => 'OrderedCollectionPage',
                     'partOf' => 'https://example.com/objects/1',
                     'startIndex' => 3,
                     'orderedItems' => array(
-                        array(
-                            'id' => 'https://example.com/objects/5',
-                        ),
-                        array(
-                            'id' => 'https://example.com/objects/6',
-                        ),
-                    ),
-                ),
-            ),
-            array(
-                'id' => 'nonExistentPage',
-                'collection' => array(
-                    '@context' => array(
-                        'https://www.w3.org/ns/activitystreams',
-                        'https://w3id.org/security/v1',
-                    ),
-                    'id' => 'https://example.com/objects/1',
-                    'type' => 'OrderedCollection',
-                    'orderedItems' => array(
-                        array(
-                            'id' => 'https://example.com/objects/2',
-                        ),
                         array(
                             'id' => 'https://example.com/objects/3',
                         ),
                         array(
-                            'id' => 'https://example.com/objects/4',
+                            'id' => 'https://example.com/objects/2',
                         ),
-                    )
+                    ),
                 ),
-                'request' => Request::create(
-                    'https://example.com/objects/1?offset=3',
-                    Request::METHOD_GET
-                ),
-                'expectedException' => NotFoundHttpException::class,
             ),
             array(
                 'id' => 'authFilteringPublic',
@@ -301,20 +274,20 @@ class CollectionsServiceTest extends APTestCase
                             'https://www.w3.org/ns/activitystreams',
                             'https://w3id.org/security/v1',
                         ),
-                        'id' => 'https://example.com/objects/1?offset=0',
+                        'id' => 'https://example.com/objects/1?offset=0&sort=desc',
                         'type' => 'OrderedCollectionPage',
                         'partOf' => 'https://example.com/objects/1',
                         'startIndex' => 0,
                         'orderedItems' => array(
                             array(
-                                'id' => 'https://example.com/objects/3',
+                                'id' => 'https://example.com/objects/5',
                             ),
                             array(
                                 'id' => 'https://example.com/objects/4',
                                 'to' => 'https://www.w3.org/ns/activitystreams#Public',
                             ),
                             array(
-                                'id' => 'https://example.com/objects/5',
+                                'id' => 'https://example.com/objects/3',
                             ),
                         ),
                     ),
@@ -369,7 +342,144 @@ class CollectionsServiceTest extends APTestCase
                             'https://www.w3.org/ns/activitystreams',
                             'https://w3id.org/security/v1',
                         ),
-                        'id' => 'https://example.com/objects/1?offset=0',
+                        'id' => 'https://example.com/objects/1?offset=0&sort=desc',
+                        'type' => 'OrderedCollectionPage',
+                        'partOf' => 'https://example.com/objects/1',
+                        'startIndex' => 0,
+                        'orderedItems' => array(
+                            array(
+                                'id' => 'https://example.com/objects/6',
+                                'to' => 'https://example.com/actors/2',
+                            ),
+                            array(
+                                'id' => 'https://example.com/objects/5',
+                            ),
+                            array(
+                                'id' => 'https://example.com/objects/4',
+                                'to' => 'https://www.w3.org/ns/activitystreams#Public',
+                            ),
+                            array(
+                                'id' => 'https://example.com/objects/3',
+                            ),
+                        ),
+                    ),
+                ),
+            ),
+            array(
+                'id' => 'sortAsc',
+                'collection' => array(
+                    '@context' => array(
+                        'https://www.w3.org/ns/activitystreams',
+                        'https://w3id.org/security/v1',
+                    ),
+                    'id' => 'https://example.com/objects/1',
+                    'type' => 'OrderedCollection',
+                    'orderedItems' => array(
+                        array(
+                            'id' => 'https://example.com/objects/2',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/3',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/4',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/5',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/6',
+                        ),
+                    )
+                ),
+                'request' => Request::create(
+                    'https://example.com/objects/1?sort=asc',
+                    Request::METHOD_GET
+                ),
+                'expectedResult' => array(
+                    '@context' => array(
+                        'https://www.w3.org/ns/activitystreams',
+                        'https://w3id.org/security/v1',
+                    ),
+                    'id' => 'https://example.com/objects/1',
+                    'type' => 'OrderedCollection',
+                    'first' => array(
+                        '@context' => array(
+                            'https://www.w3.org/ns/activitystreams',
+                            'https://w3id.org/security/v1',
+                        ),
+                        'id' => 'https://example.com/objects/1?offset=0&sort=asc',
+                        'type' => 'OrderedCollectionPage',
+                        'partOf' => 'https://example.com/objects/1',
+                        'startIndex' => 0,
+                        'next' => 'https://example.com/objects/1?offset=4&sort=asc',
+                        'orderedItems' => array(
+                            array(
+                                'id' => 'https://example.com/objects/2',
+                            ),
+                            array(
+                                'id' => 'https://example.com/objects/3',
+                            ),
+                            array(
+                                'id' => 'https://example.com/objects/4',
+                            ),
+                            array(
+                                'id' => 'https://example.com/objects/5',
+                            ),
+                        ),
+                    ),
+                ),
+            ),
+            array(
+                'id' => 'authFilteringSpecificActorSortAsc',
+                'collection' => array(
+                    '@context' => array(
+                        'https://www.w3.org/ns/activitystreams',
+                        'https://w3id.org/security/v1',
+                    ),
+                    'id' => 'https://example.com/objects/1',
+                    'type' => 'OrderedCollection',
+                    'orderedItems' => array(
+                        array(
+                            'id' => 'https://example.com/objects/2',
+                            'to' => 'https://example.com/actors/1',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/3',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/4',
+                            'to' => 'https://www.w3.org/ns/activitystreams#Public',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/5',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/6',
+                            'to' => 'https://example.com/actors/2',
+                        ),
+                    )
+                ),
+                'request' => Request::create(
+                    'https://example.com/objects/1?sort=asc',
+                    Request::METHOD_GET
+                ),
+                'requestAttributes' => array(
+                    'actor' => 'https://example.com/actors/2',
+                ),
+                'expectedResult' => array(
+                    '@context' => array(
+                        'https://www.w3.org/ns/activitystreams',
+                        'https://w3id.org/security/v1',
+                    ),
+                    'id' => 'https://example.com/objects/1',
+                    'type' => 'OrderedCollection',
+                    'first' => array(
+                        '@context' => array(
+                            'https://www.w3.org/ns/activitystreams',
+                            'https://w3id.org/security/v1',
+                        ),
+                        'id' => 'https://example.com/objects/1?offset=0&sort=asc',
                         'type' => 'OrderedCollectionPage',
                         'partOf' => 'https://example.com/objects/1',
                         'startIndex' => 0,
@@ -392,8 +502,60 @@ class CollectionsServiceTest extends APTestCase
                     ),
                 ),
             ),
+            array(
+                'id' => 'nonExistentPage',
+                'collection' => array(
+                    '@context' => array(
+                        'https://www.w3.org/ns/activitystreams',
+                        'https://w3id.org/security/v1',
+                    ),
+                    'id' => 'https://example.com/objects/1',
+                    'type' => 'OrderedCollection',
+                    'orderedItems' => array(
+                        array(
+                            'id' => 'https://example.com/objects/2',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/3',
+                        ),
+                        array(
+                            'id' => 'https://example.com/objects/4',
+                        ),
+                    )
+                ),
+                'request' => Request::create(
+                    'https://example.com/objects/1?offset=3',
+                    Request::METHOD_GET
+                ),
+                'expectedException' => NotFoundHttpException::class,
+            ),
         );
         foreach ( $testCases as $testCase ) {
+            $this->authService = new AuthService();
+            $contextProvider = new ContextProvider();
+            $httpClient = $this->getMock( Client::class );
+            $httpClient->method( 'send' )->willReturn(
+                new Psr7Response( 200, array(), json_encode( array(
+                    'type' => 'OrderedCollectionPage',
+                    'orderedItems' => array(
+                        'item3',
+                        'item4',
+                    ),
+                ) ) )
+            );
+            $entityManager = $this->getMock( EntityManager::class );
+            $collection = $testCase['collection'];
+            $objectsService = $this->getMock( ObjectsService::class );
+            $objectsService->method( 'update' )->willReturn( TestActivityPubObject::fromArray( $collection ) );
+            $this->collectionsService = new CollectionsService(
+                4,
+                $this->authService,
+                $contextProvider,
+                $httpClient,
+                new SimpleDateTimeProvider(),
+                $entityManager,
+                $objectsService
+            );
             if ( array_key_exists( 'expectedException', $testCase ) ) {
                 $this->setExpectedException( $testCase['expectedException'] );
             }