1. Rats after a 24 h restraint developed acute gastric erosions. Cimetidine in a dose of 100 mg/kg body weight was given subcutaneously every 8 h to a group of 150 rats after restraint. A second group received saline subcutaneously (placebo group). 2. Erosions in the placebo group required up to 45 days to heal (median healing time approximately 24 days). Cimetidine treatment reduced the median healing time to approximately 12 days. 3. Cimetidine in this dose promotes healing of acute gastric erosions in the rat induced by restraint.