The biological activity of cow IgG administered orally to 11 volunteers in the colostrum of cows vaccinated with Sh. sonnei was studied. At the same time the degree of immunologic protection was determined on the experimental model of pepsin fragments of this IgG active against Sh. sonnei. IgG, introduced orally, could be regularly found in gastric and intestinal juices, as well as in coprofiltrates. A decrease in the concentration of IgG and related antibodies was observed as this IgG moved down along the digestive tract: the maximum loss of biological activity occurred in the lower sections of the intestine. The products of pepsin hydrolysis of immune cow IgG ensure pronounced protection against Sh. sonnei. The preservation of the biological activity of IgG in the digestive secretions of adults receiving immune colostrum orally indicates the expediency of further studies in the field of passive enteral immunization for the prevention and treatment of acute intestinal diseases.