We evaluated the hypothesis that characterological factors, particularly antisocial personality, influence scores on the MacAndrew Alcoholism Scale (MAC). Using the Washington University research criteria to establish diagnoses, the following subgroups were defined: subjects who received no psychiatric diagnoses; subjects who received diagnoses other than alcoholism, drug dependence, or antisocial personality; and subjects who received a diagnosis of alcoholism, drug dependence, and/or antisocial personality, alone or in combination with other psychiatric diagnoses. The highest MAC scores were obtained by subjects diagnosed as having antisocial personality without alcoholism or drug dependence and subjects diagnosed with antisocial personality, drug dependence, and alcoholism. Alcoholics without antisocial personality or drug dependence, and subjects with other psychiatric diagnoses scored lowest. Although higher MAC scores were obtained by males, MAC scores greater than 24 correctly classified the greatest number of males and females as alcoholic, drug dependent and/or antisocial. These findings are interpreted as consistent with MacAndrew's reinterpretation of the scale as assessing a dimension of personality, rather than solely a tendency to addiction.