Cord blood levels of immunoglobulin (Ig) A, IgM, IgD, and IgG classes and IgA and IgA subclasses were determined in the offspring of seven mothers who received azathioprine and/or prednisone during the entire pregnancy. Five of these women received the immunosuppressive therapy following kidney transplantation, and two received immunosuppressive therapy because of disseminated systemic lupus erythematosus. The fetuses appeared to have intact humeral immune function in that they had normal cord blood immunoglobulin concentrations and in one case responded with increased synthesis of IgA and IgM following premature rupture of the membranes.