In this issue we present an exchange of views arising from the DSM-IV diagnostic criteria for delusions. Anchoring the discussion is an article by Drs. Mujica-Parodi and Sackeim in which they examine the DSM-IV requirement that to be classified as a delusion, a belief must be discordant with beliefs ordinarily accepted by the patient's culture or subculture. They propose that an information-processing model would avoid what they regard as the relativism and ambiguity of this DSM-IV criterion. Drs. Cutting and Fabrega critique the model and reflect further on the diagnosis of delusions, and the authors reply.