We studied bipolar (ever manic; n = 297) primary unipolar (never secondary; n = 328), and secondary unipolar (n = 241) RDC major affective disorder patients in the NIMH--CRB Collaborative Study of the Psychobiology of Depression--Clinical. We examined rates of immigration, for patients and their parents, in these three diagnostic groups. Primary patients had a twofold increase in the odds in favor of immigration, compared to secondary patients. The difference persisted when proband age was statistically controlled, and could not be accounted for by any difference in sex ratios between groups. Previous findings of an increased rate of immigration in bipolar patients could not be replicated.