A collection of items may be categorized according to a category hierarchy. A search of the items may be explicitly associated with a particular category in the hierarchy or else unassociated. A set of refinements may be available, for example, to help narrow the search. Refinements may be applicable to items in linked categories. Refinements may be surfaced based at least in part on linked categories associated with the search. Refinements may be surfaced when the search is unassociated with a particular category. For example, a possibly relevant set of categories may be determined. Refinements may be surfaced according to a variety of ordering criteria.