Abstract: The pharmacological function of nacrum secreted by cultured pallium cells of a freshwater oyster was examined.Injections of the cultured mantle tissue solution into micecan reduce the bleeding duration after their tails being cut.The cultured solution and thehydrolysed cultured solution can strengthen the systole of the rat uterus(in vitro)andthe toad heart(in vitro),but suppress the systole of rabbit small in testine. Thispharmacological function changes with taurine content in the cuItured solution. The results indicate that the oyster cells secret nacrum vigorously under culturedconditions in vitro,and the secreted nacrum has the same pharmacological function asthe natural pearls.