Calpastatin is an endogenous inhibitor of the calpain (EC.3.4.22.17, Ca+-dependent cysteine proteinase) proteolytic enzyme system, which plays a major role in the postmortem tenderization.Complementary strand DNA of calpastatin gene derived from domain I of Longissimus dorsi muscle from Kamphaeng Saen beef breed was amplified using the 1AF_1DR primer.