This study examined whether changes in diagnostic criteria from the DSM-III to the DSM-III for personality disorders (PDs) had the intended effects. Seventy-two subjects at the University of Iowa from three research studies and one clinical sample were administered two structured interviews (the Structured Interview for DSM-III Personality [SIDP] and the revised SIDP [SIDP-R]) to assess DSM-III and DSM-III-R criteria. Major changes in rates of diagnoses were observed between the DSM-III and DSM-III-R criteria with kappas for agreement ranging between -.025 and .571. As expected, the switch from monothetic to polythetic definitions had an effect on which patients were assigned a given diagnosis. However, not all of the other revisions associated with the DSM-III-R had the intended effects. For instance, the frequency of the diagnosis of schizoid PD did not increase, nor did the overlap between borderline and histrionic PDs decrease. In addition, there was an unintended increase in the rate of paranoid PD. An analysis of individual criteria showed how small, apparently minor changes in the wording of criteria can sometimes have major effects on which patients received a diagnosis of PD.