The differential prevalence of the histrionic and antisocial personality disorders among men and women has been attributed both to sex biases and to actual variation in disorder base rates. The present study assessed the bias and base rate explanations and examined whether sex biases are minimized by the relatively explicit diagnostic criteria in the DSM-III. Psychologists (N = 354) either diagnosed 9 DSM-III disorders from case histories that varied in the ambiguity of the antisocial and histrionic personality disorder diagnoses or rated the degree to which specific features extracted from the case histories met 10 histrionic and antisocial diagnostic criteria. The sex of the patient was either male, female, or unspecified. Sex biases were evident for the diagnoses but not for the diagnostic criteria. The results are discussed with respect to base rate effects, sex biases, and the construction of diagnostic criteria.