A stress method in mice which develops gastric erosions was devised. This stress procedure consisted of restraint and water immersion. Maximal development of gastric erosions was observed when mice were restrained and immersed at 25°C for 18 hr. There was no apparent sex difference in the susceptibility to this method. Drug study was performed to evaluate the drug sensitivity of this stress method. From the results, it can be concluded that this stress method is a good testing ground for drug sensitivity.Conclusively, the present stress method in mice is suggested to be of advantage in studying gastric ulceration and evaluating the ability of drugs to inhibit gastric erosions.