A set of guidelines is proposed for the possible inclusion or exclusion of diagnostic categories in the DSM-IV. For possible inclusion, a new category should meet all of the following five guidelines: adequate literature, specified diagnostic criteria, acceptable interclinician reliability, evidence that the criteria forms a syndrome, and differentiation from other categories. For possible exclusion, a category should possess an inadequate literature, extremely low coverage, or evidence of diagnostic bias. None of the exclusionary guidelines would be invoked if the category refers to a demonstrable disease.