To delineate homogenous subgroups among hospitalized opiate addicts, a multivariate correlational clustering technique was applied to the Minnesota Multiphasic Personality Inventory profiles of 1,500 addicts, subdivided into 10 subsamples (5 for each sex) representing four different categories of admission into treatment (civilly committed, volunteers, probationers, prisoners). Within each subsample, two homogeneous and replicable profile types were isolated. Type I (33% of all addicts) showed elevations on Scales 2, 4, and 8, suggesting marked subjective distress, nonconformity, and disturbed thinking. The much smaller Type II (about 7% of addicts) showed a single peak on Scale 4. Sixty percent of addicts thus were unclustered. The two basic types, however, were very effectively discriminated on a variety of other psychometric indexes and were consistent with the two major profile types found among alcoholics in prior research. Recent psychometric characterizations of hospitalized opiate addicts, employing the Minnesota Multiphasic Personality Inventory (MMPI), have cast doubt on the relevance of the stereotype of sociopathy (the 4-9 or 9-4 profile) to addicts as a group (Berzins, Ross, & Monroe, 1971). A grand mean MMPI profile with peaks on Scales 4, 2, and 8, obtained in a sample of over 800 male addicts, for example, placed the addicts' nonconformity in the context of acute subjective distress and disturbed thinking. It is important, however, to determine the principal homogeneous subgroups of addicts whose characteristics may or may not be consistent with overall group profiles. The number, size, and nature
