This study examines the ability of the MacAndrew Alcoholism Scale (MAC) to indicate drug abuse among adolescents. Comparisons of MAC scores were made among four groups of adolescents: (a) 135 unselected high school students (76 female, 59 male); (b) inpatient psychiatry patients of a major teaching hospital (43 female, 47 male), who had no significant history of substance abuse; (c) outpatient psychiatry and psychology clinic patients at the same hospital (43 female, 38 male), who had no significant history of substance abuse; and (d) 100 randomly selected clients (50 female, 50 male) at a residential treatment center for drug-abusing adolescents. Mean MAC score differences among groups were demonstrated for male and female adolescents. Comparisons of differences between pairs of means indicated that MAC mean scores were similar for female high school students and psychiatry patients and significantly higher for substance-abusing female adolescents. For male subjects, mean MAC score differences were demonstrated between substance-abusing adolescents and high school students and between substance abusers and psychiatric outpatients, but mean MAC score differences between substanceabusing and psychiatric inpatient adolescent males were not significant. An attempt to determine optimal MAC cutting scores for all groups resulted in suggested cutting scores > 24 for female subjects and > 26 for male subjects.According to a survey by the National Institute of Drug Abuse (Fishburne, Abelson, & Cisin, 1979), the number of adolescents using drugs and alcohol has nearly doubled over the last decade. An objective means of identifying those adolescents who are substance abusers, when incorporated into the history and interview procedures currently in use, could result in more accurate evaluations and timely interventions.Scores on the MacAndrew Alcoholism Scale (MAC) have successfully differentiated adult male alcoholics from nonalcoholic psychiatric patients (DeGroot & Adamson, 1973;MacAndrew, 1965;Rhodes, 1969;Whisler & Cantor, 1966), young male alcohol-related offenders from psychiatric patients and from college students (MacAndrew, 1979), and adult female alcoholics from nonalcoholic female psychiatric patients (Rich & Davis, 1969;Schwartz & Graham, 1979). There is also evidence that the MAC differentiates heroin addicts and polydrug users from nonaddicts with Requests for reprints should be sent to