diff --git a/data/model/repository.py b/data/model/repository.py
index 4684bc8af..6602bc081 100644
--- a/data/model/repository.py
+++ b/data/model/repository.py
@@ -181,49 +181,50 @@ def garbage_collect_repo(repo, extra_candidate_set=None):
     logger.debug('No candidate images for GC for repo: %s', repo.id)
     return True
 
-  candidates_orphans = list(candidate_orphan_image_set)
+  all_images_removed = set()
+  all_storage_id_whitelist = set()
+  all_unreferenced_candidates = set()
 
-  with db_transaction():
-    Candidate = Image.alias()
-    Tagged = Image.alias()
-    ancestor_superset = Tagged.ancestors ** db_concat_func(Candidate.ancestors, Candidate.id, '/%')
+  # Iteratively try to remove images from the database. The only images we can remove are those
+  # that are not referenced by tags AND not the parents of other images. We continue removing images
+  # until no changes are found.
+  iteration = 0
+  while candidate_orphan_image_set:
+    iteration = iteration + 1
+    logger.debug('Starting iteration #%s for GC of repository %s with candidates: %s', iteration,
+                 repo.id, candidate_orphan_image_set)
+    candidates_orphans = list(candidate_orphan_image_set)
 
-    # We are going to compute all images which are being referenced in two ways:
-    # First, we will find all images which have their ancestor paths appear in
-    # another image. Secondly, we union in all of the candidate images which are
-    # directly referenced by a tag. This can be used in a subquery to directly
-    # find which candidates are being referenced without any client side
-    # computation or extra round trips.
-    direct_referenced = (RepositoryTag
-                         .select(RepositoryTag.image)
-                         .where(RepositoryTag.repository == repo.id,
-                                RepositoryTag.image << candidates_orphans))
-
-    cloned = direct_referenced.clone().alias('direct_ref')
-    directly_referenced_subquery = Image.alias().select(cloned.c.image_id).from_(cloned)
-
-    ancestor_referenced = (Candidate
-                           .select(Candidate.id)
-                           .join(Tagged, on=ancestor_superset)
-                           .join(RepositoryTag, on=(Tagged.id == RepositoryTag.image))
+    with db_transaction():
+      # Any image directly referenced by a tag that still exists, cannot be GCed.
+      direct_referenced = (RepositoryTag
+                           .select(RepositoryTag.image)
                            .where(RepositoryTag.repository == repo.id,
-                                  Candidate.id << candidates_orphans,
-                                  ~(Candidate.id << directly_referenced_subquery)))
+                                  RepositoryTag.image << candidates_orphans))
 
-    referenced_candidates = (direct_referenced | ancestor_referenced)
+      # Any image which is the parent of another image, cannot be GCed.
+      parent_referenced = (Image
+                           .select(Image.parent)
+                           .where(Image.repository == repo.id,
+                                  Image.parent << candidates_orphans))
 
-    # We desire a few pieces of information from the database from the following
-    # query: all of the image ids which are associated with this repository,
-    # and the storages which are associated with those images.
-    unreferenced_candidates = (Image
-                               .select(Image.id, Image.docker_image_id,
-                                       ImageStorage.id, ImageStorage.uuid)
-                               .join(ImageStorage)
-                               .where(Image.id << candidates_orphans,
-                                      ~(Image.id << referenced_candidates)))
+      referenced_candidates = (direct_referenced | parent_referenced)
+
+      # We desire a few pieces of information from the database from the following
+      # query: all of the image ids which are associated with this repository,
+      # and the storages which are associated with those images.
+      unreferenced_candidates = (Image
+                                 .select(Image.id, Image.docker_image_id,
+                                         ImageStorage.id, ImageStorage.uuid)
+                                 .join(ImageStorage)
+                                 .where(Image.id << candidates_orphans,
+                                        ~(Image.id << referenced_candidates)))
+
+      image_ids_to_remove = [candidate.id for candidate in unreferenced_candidates]
+      if len(image_ids_to_remove) == 0:
+        # No more candidates to remove.
+        break
 
-    image_ids_to_remove = [candidate.id for candidate in unreferenced_candidates]
-    if len(image_ids_to_remove) > 0:
       logger.info('Cleaning up unreferenced images: %s', image_ids_to_remove)
       storage_id_whitelist = set([candidate.storage_id for candidate in unreferenced_candidates])
 
@@ -253,15 +254,22 @@ def garbage_collect_repo(repo, extra_candidate_set=None):
         logger.info('Could not GC images %s; will try again soon', image_ids_to_remove)
         return False
 
+      # Add the images to the removed set and remove them from the candidate set.
+      all_images_removed.update(image_ids_to_remove)
+      all_storage_id_whitelist.update(storage_id_whitelist)
+      all_unreferenced_candidates.update(unreferenced_candidates)
+
+      candidate_orphan_image_set.difference_update(image_ids_to_remove)
+
   # If any images were removed, GC any orphaned storages.
-  if len(image_ids_to_remove) > 0:
-    logger.info('Garbage collecting storage for images: %s', image_ids_to_remove)
-    storage_ids_removed = set(storage.garbage_collect_storage(storage_id_whitelist))
+  if len(all_images_removed) > 0:
+    logger.info('Garbage collecting storage for images: %s', all_images_removed)
+    storage_ids_removed = set(storage.garbage_collect_storage(all_storage_id_whitelist))
 
     # If any storages were removed and cleanup callbacks are registered, call them with
     # the images+storages removed.
     if storage_ids_removed and config.image_cleanup_callbacks:
-      image_storages_removed = [candidate for candidate in unreferenced_candidates
+      image_storages_removed = [candidate for candidate in all_unreferenced_candidates
                                 if candidate.storage_id in storage_ids_removed]
       for callback in config.image_cleanup_callbacks:
         callback(image_storages_removed)