The effects of moderate maternal protein restriction on in vivo humoral and cell-mediated immune responses of bovine neonates were studied. Hereford heifers were fed protein-adequate or protein-restricted rations for the last 150 days of gestation and for 6 months after parturition. At birth, all calves from these heifers were allowed to remain with their dams and were inoculated with tetanus toxoid (TT) and an emulsion of tuberculoproteins and trehalose dimycolate (cord factor) of Mycobacterium bovis. One month later, blood samples were collected from all calves, and sera were examined for antibodies to TT. The calves were given a 2nd inoculation of TT, and anamnestic antibody responses were measured 7 days later. Differences in primary or secondary antibody responses were not observed between principal and control groups of calves. Also, differences in tuberculin reactivity were not observed in calves from cows fed protein-adequate or protein-restricted diets.