The effects of total saponins of Semen Ziziphi spinosae (ZS) were observed on cultured neonatal rat myocardial cells injured by deprivation of oxygen and glucose (DOG) or treatment with chlorpromazine (CPZ) and mitomycin C (MMC). The increases of lactate dehydrogenase release from damaged myocardial cells induced by DOG, CPZ and MMC were attenuated by ZS (33 micrograms/ml) except 11 micrograms/ml which showed no effect on MMC (24 h) and CPZ (9 h)-induced injuries. These data suggest that ZS is an effective protective drug for myocardial cells.