Progeny and maternal immune status after benzo(a)pyrene (BP) exposure of mothers at mid-pregnancy is disrupted in fetal liver (FL), in spleen and in thymus during pregnancy and postnatally. Mice suffer deficiencies in splenic and thymic mixed lymphocyte responses (MLR), and disorientations of T antigen expressing cells, punctuated by exorbitant increases in Lyt2, especially in FL. FL Lyt2 do not suppress an MLR, while Lyt1 mediate suppression. Isolated Thy1 show a weak response to Concanavalin A; FL Thy1 weakly express an MLR. Maternal macrophages and progeny B cells are also functionally abnormal. Thus, BP induces generalized immune deficiency that may affect ontogeny and which is potentially deleterious to health.