The occurrence of sarcocystosis was studied in the sheep produced in the vicinity of Brno and killed in the slaughterhouse. Adspection, the homogenization method and the digestion method were used for the detection of muscular cysts. Antibodies to sarcocystosis were determined in the blood serum by the indirect fluorescence method. The total number of sheep examined was 157; sarcocysts were detected in the muscle of 102 sheep (64.9%). The highest incidence was recorded in ewes: 60 ewes (80%) out of 75 were positive. Out of the 157 blood serum samples examined by the indirect fluorescence method, antibodies were found in 105 samples (66.9%). The antibody response was 77.3% in ewes, 63.4% in lambs and 46.6% in rams. The highest titres (640-10 240) were obtained in 16 lambs and 26 ewes.