The authors studied 442 probands with nonbipolar major depression, 64 with bipolar II disorder, and 88 with bipolar I disorder. Although the proband groups did not differ in occupational or educational achievement, the first-degree relatives of probands with bipolar disorders had significantly higher mean levels of achievement than did those of probands with nonbipolar disorder. This pattern applied whether or not the relatives themselves had bipolar illness. The authors conclude that the socioeconomic advantage previously associated with affective disorder in general may be limited to the bipolar forms.