The MMPI Personality Disorder scales, developed by Morey, Waugh, and Blashfield (1985), were validated on an inpatient population by comparing 104 patients' MMPI-PD scores with the MCMI and with DSM-III-R diagnosis. Conservative significance levels were used to ensure more valid conclusions. Schizoid, Avoidant, Dependent, Histrionic, and Narcissistic scales were correlated significantly. Passive-Aggressive, Schizotypal, and Borderline scales did not correlate with corresponding MCMI scales. The MMPI-PD nonoverlapping scales were most effective in predicting diagnosis, specifically the Personality Disorder NOS, Eccentric and Borderline groups. The overlapping scales were not as effective in predicting diagnosis, but best predicted the Eccentric and Borderline groups. This study provides support for the validity of specific scales and circumscribed diagnostic utility for both measures.