Summary: Low molecular weight (6.6S) diphtheria and tetanus antibodies of ovine origin were absorbed relatively efficiently through the intestine of newborn, colostrum-deprived pigs, whereas high molecular weight (18S) antibodies were absorbed poorly or not at all. Antibodies contained in 750 mg of purified 6.6S ovine globulin, administered orally and intraperitoneally, were eliminated from the circulation of newborn pigs at a constant exponential rate. The 6.6S globulin did not stimulate the production of anti-sheep globulin by the recipient pigs. Intraperitoneal administration of 750 mg of crude ovine globulin, containing antibodies in both the 6.6S and 18S fractions, resulted in an immune-type elimination of the passive antibodies by the recipient newborn pigs. This treatment resulted in the production of anti-sheep globulin by the recipient pigs. Dilute 6.6S ovine antitoxin, premixed with toxoid and injected intraperitoneally into 3-week-old, colostrum-deprived pigs, induced the production of relatively large quantities of tetanus and diphtheria antibodies by the recipient pigs. Dilute 18S antitoxin plus toxoid, under the same circumstances, failed to stimulate diphtheria antibody formation but resulted in the production of high titers of tetanus antibodies.