The effects of optical isomers of nicardipine on the secretion of pancreatic juice and blood flow were investigated in the dog-isolated, blood-perfused pancreas. Intra-arterial administration of (-)-nicardipine (10-300 micrograms) caused a dose-dependent increase in pancreatic secretion. However, the (+)-isomer was much less potent than the (-)-isomer and even in 300 micrograms of (+)-isomer caused only a slight secretion. (+)- And (-)-nicardipine increased perfusion blood flow in a dose-dependent manner, and (+)-nicardipine was approximately five times as potent as the (-)-isomers. The maximum increase in a flow rate was produced by 30 micrograms of (+)-isomer and 100 micrograms of (-)-isomer. Bicarbonate concentration in pancreatic juice induced by (-)- and (+)-nicardipine was increased in a dose-dependent manner, but the protein concentration was only increased slightly. From these results, it is concluded that there is a stereoselectivity in the secretory and vascular actions of optical isomers of nicardipine.