A search server is configured to return secondary content associated with primary content determined to be relevant to a search query. One or more databases store: (1) information identifying primary content items returnable as search results, (2) information identifying secondary content items, and (3) data identifying associations among the primary content items and the secondary content items. When the search server receives a search query, the one or more databases are queried to identify primary content items relevant to the search query. Additionally, the one or more databases are queried to identify secondary content items associated with the identified primary content items. The secondary content items can be selected based on a number of the identified primary content items associated with each secondary content item in the one or more databases. The identified primary content items and selected secondary content items are returned as a response to the search query.