Pharmacokinetics of iodine containing and native lactoferrin from human milk was studied in intact mice and the animals with Ehrlich ascites carcinoma. Both these antigens, native and I-lactoferrin, were similarly distributed in intact mice body. The same pharmacokinetics was found in tumor-bearing animals. Exogenous lactoferrin penetrated mainly into liver tissue, then simultaneously with bile--into small intestine and further into large intestine. Distinct accumulation of the glycoprotein was not found in tumor tissue.