This study compares the clinical relevance and utility of five dimensional diagnostic systems for personality disorders that have been proposed for the forthcoming edition of DSM (DSM-V): (1) a criteria counting model based on current DSM-IV diagnostic criteria; (2) a prototype matching model based on current DSM-IV diagnostic criteria; (3) a prototype matching model based on the Shedler-Westen Assessment Procedure (SWAP); (4) the Five Factor Model; and (5) Cloninger's Psychobiological Model. A random national sample of psychiatrists and psychologists applied all 5 diagnostic systems to a patient in their care and rated the clinical utility of each system. The SWAP Prototype Matching and DSM-IV Prototype Matching models were judged most clinically useful and relevant. The Five Factor Model and Cloninger's Psychobiological Model were judged least useful. The prototype matching systems most faithfully capture the personality syndromes seen in clinical practice, and permit rich descriptions of diagnostic constructs without a proportionate increase in user effort. A prototype matching approach to personality diagnosis deserves consideration for DSM-V.