Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, re-ranking resources for categorical queries. In one aspect, a method includes receiving queries, and for each received query: receiving data indicating resources identified by a search operation as being responsive to the query and ranked according to a first order, each resource having corresponding search score by which the resources are ranked in responsiveness to the query and determining whether a proper subset meets a quality condition based on a quality measure that is indicative of the quality of the resources in the proper subset and independent of search scores of the resources for received query. For each query for which the proper subset meets the quality condition, determining a quality score for each resource in the proper subset and re-ranking the resources in the proper subset according to their respective quality scores.