The alcoholic drug-dependent patients (n = 169, 51.4 percent) were than compared with the nonalcoholic patients (n = 160, 48.6 percent) with regard to sociodemographic, clinical and family history characteristics. The alcoholics were significantly more likely to receive a DSM-III diagnosis of major depression, with melancholia; other Axis I diagnoses were equally distributed between the two groups. Antisocial personality disorder was also significantly more prevalent among the alcoholic patients. The alcoholics had somewhat longer drug histories and more vivid memories of their first drinking experiences; polydrug abuse, however, was no more common in this group. Finally, the first-degree relatives of the alcoholics had significantly more alcoholism than the first-degree relatives of the nonalcoholic patients. Implications regarding the relationship of alcoholism and other forms of substance abuse are discussed. 39 references, 4 tables. (Author abstract)