Electron microscopic examination was performed to show the effects of interferon-alpha (IFN-alpha) on Paneth and goblet cells in rat intestines. After the administration of IFN-alpha (70,000 IU/kg), many cells of both types were depleted of secretory granules and their apical membranes had the deep cavitation that accompanies recent compound exocytotic activity. These results may indicate the involvement of these cells in the inflammatory reactions via IFN-alpha and this model provides a powerful tool to study differential effects of IFN-alpha on Paneth and goblet cells.