Paranoid personality disorder (PPD) is currently included in DSM-IV's "odd cluster" or "cluster A." In the present article, the authors review available information pertaining to the psychometric properties of PPD, as derived from the relevant literature and from databases of personality disorder study groups. There is comparatively little published evidence for the reliability and validity of PPD, and researchers by and large have tended not to study the disorder, either because of investigators' difficulty recruiting individuals with PPD into research studies, or (as seems more likely) because the trait-paranoia from which many psychiatric patients suffer has seemed better explained by other DSM-IV disorders on Axis I and/or Axis II than by PPD. Given the scant empirical evidence on PPD, it seems reasonable to remove it as an independent diagnosis from the next edition of DSM, and instead to encourage clinicians to code trait-paranoia using a dimensional approach.