Five hundred and forty-eight samples of pig heart muscle were collected from the abattoirs of many regions in Korea to reveal the frequency of Sarcocystis infections and to identify the species from June 1988 to April 1989. Heart muscle of the pigs was inspected for sarcocysts by the direct detection technique and for bradyzoites by the trypsin digestion technique. For examination of development of the parasites in the final host, 5 cross bred mature dogs, 5 puppies and 5 kittens were fed 100g, 50g and 50g of the infected meat respectively, four times in 2 days. Of 402 fattened and 146 older culled breeding pigs, 3 fattened pigs and 39 culled pigs were positive for Sarcocystis. Sarcocystis cysts from heart muscle measured an average of 425 x 169 micro m and bradyzoites an average of 15.6 x 3.5 micro m. Of 15 animals, only 2 puppies were infected with Sarcocystis. The prepatent period was 11 to 12 days and patent period was not examined since the puppies were infected with some another infections and one died on day 11 and another died on day 12 after ingestion of the meat. The sporulated oocysts were detected 11 days after ingestion of the meat and sporocysts 12 days from the puppy feces. The sporulated oocysts measured an average of 16.5 x 11.5 micro m and sporocysts an average of 12.6 x 7.9 micro m. On scaping examination of the intestinal mucosa, fully sporulated oocysts were detected in the tip of the intestinal villi. Considering above all descriptions, Sarcocystis in pig heart muscle in Korea was identified with Sarcocystis suicanis