This study used a multi-sample, multiple-instrument strategy to evaluate the hypothesis that schizotypal personality disorder (SPD) is taxonic. In Study 1, 721 consecutively admitted inpatients and outpatients were evaluated with the Structured Clinical Interview for DSM-IV Axis II Personality Disorders (SCID-II) and the Personality Diagnostic Questionnaire-4+ (PDQ-4+). The data from both questionnaire types were submitted to multivariate normal mixture analysis, which was carried out on factor scores obtained from a three-factor model of SPD criteria; these results supported the hypothesis that SPD is taxonic. The same was true of Study 2, which administered the Semi-structured Interview for DSM-III-R Personality Disorders (SIDP-R) to an independent sample of 537 consecutively admitted outpatients. Similar findings were observed in Study 3, in which the SIDP-R was administered to 225 non-clinical subjects. The results show that the typology of DSM III-R and -IV SPD diagnosis is consistent with the latent structure of SPD features.