We have studied the effect of cyclosporine on the exocrine pancreas of rats submitted to treatment with different parenteral doses (15, 30, 50 mg/kg/day) for different time periods (7 and 30 days). Serum amylase levels, pancreas weight, and total pancreatic amylase and protein content showed a dose-dependent decrease. Basal amylase secretion from isolated lobules remained unchanged. Furthermore, the pancreatic lobules from animals under cyclosporine treatment exhibited a decreased response to bethanechol stimulation. Our data suggest that cyclosporine produces a toxic effect on exocrine pancreatic function.