Methadone client volunteers completed the Minnesota Multiphasic Personality Inventory (MMPI; Hathaway & McKinley, 1967) and MMPI-2 (Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989) on consecutive days. MMPI-2 T-scores were lower by a mean of 4.7 on the clinical scales; when 5 points were added to MMPI-2 T-scores the mean difference was 2.3. Rank order of subjects on scale T-scores was not significantly different between the two instruments. High-point similarity for clinically elevated profile pairs ranged from 61% to 92%, depending upon definition of similarity.