The immunologic effects of quadruple diphtheria, tetanus, pertussis, poliomyelitis aluminum phosphate adsorbed vaccine were compared with triple diphtheria, tetanus, and pertussis aluminum phosphate adsorbed vaccine alone and poliomyelitis vaccine alone. A total of 192 children who had not been previously immunized with the respective antigens were studied. The poliomyelitis antibody responses were significantly greater with quadruple vaccine than with poliomyelitis vaccine alone. The diphtheria antibody responses were greater with quadruple vaccine than with triple vaccine. The antibody responses for tetanus and pertussis were essentially the same for both vaccines.