Summary: Colostrum-deprived pigs formed tetanus, but not diphtheria antibodies following intraperitoneal inoculation of tetanus and diphtheria toxoids at birth. Colostrum-fed pigs formed diphtheria antibodies after intraperitoneal inoculation of the toxoid at birth, but their antibody response to tetanus toxoid was depressed. The interpretation of these results is discussed in the light of the assumption that a degree of transplacental transfer of maternal antibody took place and that antibodies against tetanus, but not against diphtheria are present in the sow's blood. γ-Globulin was found in the serum of newborn, colostrum-deprived pigs.