The effects of drugs on intracellular calcium concentration(［Ca2+］i) were investigated with fura-2 fluorescence technique to investigate ATP and thrombin-induced Ca2+ entry in bovine aortic endothelial cells(BAEC). It was found that application of ATP and thrombin gave rise to biphasic ［Ca2+］i elevation. ATP or thrombin only triggered a fraction of cyclopiazonic acid(CPA)-sensitive Ca2+ store, which was enough to activate Ca2+ entry. The Ca2+ release induced by thrombin resulted from the activation of phospholipase C(PLC), whereas the PLC-independent mechanism was involved in ATP-induced Ca2+ release. Nifedipine had no effect on ATP and thrombin- induced Ca2+ entry. SK&F 96365 and ginsenoside-2A inhibited both ATP and CPA-induced Ca2+ entry, however no effect of them on thrombin-induced Ca2+ entry was found. The inhibitory effects of SK&F 96365 and ginsenoside-2A on CPA-induced Ca2+ entry were less than that on ATP-induced Ca2+ entry. The Ca2+ influx sensitive to SK&F 96365 was not the same as that to ginsenoside-2A. These observations suggest that both ATP and thrombin evoke Ca2+ release and Ca2+ influx by activation of different receptor. However their mechanisms appear different.