In chase experiments, we followed the distribution of [125I]-ceruloplasmin prepared from human breast milk orally administered to young rats. Experiments were conducted using six-day-old rat pups (the embryonic type of copper metabolism) or 35-day-old ones (the adult type of copper metabolism). Using the technique of rocket immunoelectrophoresis, we have demonstrated that in six-day-old rats [125I]-ceruloplasmin was transferred from the gastrointestinal tract to the bloodstream and could be detected there over a period of 4 h. In 35-day-old rats, milk ceruloplasmin was digested in the upper part of the intestinal tract. The dynamic aspects of the distribution of labeled milk ceruloplasmin in the body of six-day old rats over a period of 4 h point out that, under the conditions of embryonic copper metabolism, it can serve as a transporter of copper ions to extrahepatic organs. We discuss the role of milk ceruloplasmin in copper metabolism in mammals during the neonatal period.