Young adult male Wistar rats (eight controls and ten experimental animals per group) were injected parenterally for 28 days: 1) cortisol or 2) cortisol and salmon calcitonin. Morphological changes of the stomach wall and enterochromaffin cells, stained immunocytochemically for serotonin, were assessed. In the group treated with cortisol superficial desquamation and erosions of the gastral mucosa were found. In this group the number of enterochromaffin cells was significantly decreased and low intensity of the immunocytochemical reaction of these cells was observed. In the cortisol-calcitonin-treated group there were no apparent changes of the gastral mucosa and the enterochromaffin cells presented a normal picture comparable to that of controls.