Multimedia information retrieval is an inherently interactive process. When the user enters a conceptual query, that is, a specification of some information need in terms of abstract concepts, there may be many alternative ways of interpreting the query. This, in turn, affects the determination ofwhat items are relevant for retrieval. In the MIRACLE system, these problems are tackled by combining abductive reasoning and dialogue planning. Whereas MIRACLE’s abductive retrieval engine is capable of deriving different interpretations of ambiguous queries, the dialogue planner employs a comprehensive conversational dialogue model for negotiating queries, clarifying information needs, and explaining retrieval results.