Immunologic responses were measured in 46 patients with lepromatous leprosy. These patients were not distinguishable from controls on the basis of responses to soluble intradermal antigens, sensitization to contactants, peripheral blood T- and B-cell percentages, in vitro lymphocyte responses to a mitogen, or the prevalence of autoantibodies. Generalized immunologic abnormalities in patients with lepromatous leprosy are neither predisposing causes nor necessary accompaniments of lepromatous leprosy, but are probably remote sequellae of the illness. By implication, the generalized immunologic abnormalities reported in other diseases are likely to be remote sequellae of the particular illness.