We studied the problems of sarcocystosis of lambs in regard to the transfer of antibodies over ewes to lambs. Antibodies in the blood serum of 26 ewes found out by help of indirect immunofluorescent reaction (NFR) varied within the range from 640 to 5120 titres, while in six cases their level was higher than in blood. In none of new-born lambs there were proved antibodies to the sarcocystosis before the drinking of colostrum but three days later we already detected antibodies in the dilution 1:4 to 1:128. Then we studied the titre dynamics of antibodies in weaned lambs. In the age of 10-18 weeks we proved only low titres of antibodies, from the 20th to the 24th weeks the titres gradually increased and from the 26th to the 30th weeks the level of antibodies increased significantly (5120 titres) with its maximum on about the 28th week. Animals had no clinic symptoms of disease. In the other part of the work we examined the muscular substance of 342 lambs, killed in the slaughter house, by a digestive method and we carried out the blood serologic examination (NFR). Microcysts were found out in 35.67% of lambs while macrocysts were so in none of them. Specific antibodies of sarcocystosis were detected in 94.44% of young animals. A high discrepancy of the both methods (61.69%) in young animals is a result of a significant antibody reaction at still undeveloped muscular cysts.