The authors reviewed the family histories of 156 patients in an affective disorders program and identified two groups of affective disorders. Group 1 consisted of bipolar illness and majon depression, with high familial incience of affective disorder and low familial incidence of alcoholism. Group 2 consisted of dysthymic disorders and secondary depression, with low familial incidence of affective disorders and high familial incidence of alcoholism. These findings do not support the common assumption that primary affective disorders and alcoholism are closely linked. The authors discuss the implications for diagnosis of depression associated with alcoholism.