The MMPI and MCMI were administered to 163 former opiate addicts who were being maintained in a methadone program affiliated with an urban hospital. Highest group mean MMPI scores were found for Psychopathic Deviate, Depression, Hypomania, and Hysteria. For the MCMI, highest group mean clinical syndrome scores were found for Drug Abuse, Alcohol Abuse, Anxiety, and Dysthymia; highest personality disorder scores were found for Antisocial, Narcissistic, Histrionic, and Paranoid. The MCMI Drug Abuse Scale identified only 49% of subjects as having a recurrent or recent history of drug abuse. Frequency and factor analyses documented the heterogeneity of the population with respect to clinical syndromes, as well as the prevalence of personality disorders (86% had elevations on MCMI Personality Scales). Factor and correlational analyses did not provide strong evidence of similar factor structure or convergent validity of the MMPI and MCMI with this population.