According to the emerging MPEG-7 standard, the seman-tic description of multimedia documents is expressed in terms of semantic entities such as objects, events, con-cepts, and fuzzy relationships among them. The above semantic entities can be used as index terms, in order to support the semantic search process. In this paper, we propose a method that associates the semantic entities with the aid of a fuzzy thesaurus. The proposed method is based on fuzzy relations and fuzzy reasoning.