The study evaluated the quality of the DSM-IV obsessive-compulsive personality disorder (OCPD) construct as a prototype category. A sample of 2237 patients from the Norwegian Network of Psychotherapeutic Day Hospitals was examined by a variety of psychometric analyses. A high number of OCPD patients (77%) had co-occurrent PDs, but only the co-occurrence with paranoid was significantly higher than expected. Exploratory factor analysis of the PD criteria indicated that OCPD consists of 2 dimensions. The first dimension, perfectionism, was constituted by OCPD criteria only and was significantly related to obsessive-compulsive disorder. The second dimension, aggressiveness, included 2 OCPD criteria, reluctance to delegate and stubbornness, but was also defined by criteria from paranoid, antisocial, and borderline PD. Confirmatory factor analysis of the OCPD criteria indicated a poor fit of both a unitary model and a 3-dimensional model. Overall, the OCPD criteria had poor psychometric properties. Although it seems that the quality of the DSM-IV OCPD as a prototype construct is insufficient, it may be improved by deleting the criteria hoarding behavior and miserliness. Alternative criteria could be related to problems in close relationships involving the need for predictability. Such revisions may add a third dimension to the 2 dimensions of perfectionism and aggressiveness.