The aim of the present study was to investigate the possibility of sex bias in the diagnostic criteria for borderline, schizotypal, avoidant, and obsessive-compulsive personality disorders. A clinical sample of 668 individuals was evaluated for personality disorder criteria using a semistructured interview, and areas of functional impairment were assessed with both self-report and semistructured interview. The authors used a regression model of bias to identify bias as differences in slopes or intercepts between men and women in the relationship between each diagnostic criterion and level of impairment. The results suggest that most of the diagnostic criteria examined do not seem to display sex bias. However, those criteria that displayed evidence of bias came largely from the borderline diagnosis.