The anti-ulcer activity of three different doses (1/10, 1/30 and 1/90 of LD50) of imipramine, amitryptyline, chlorpromazine, amphetamine, ephedrine, chlordiazepoxide and meprobamate was studied in two types of stress-produced gastric ulcers in rats. It was found that these drugs given in doses of 1/10 or 1/30 LD50 inhibited in the same degree the development of gastric ulcer-produced by the method of Senay, in spite of differences in their psychotropic activity. On the other hand, when the method of Rossi was used for ulcer production the ulcer-preventing activity of these drugs has been varied. Thymoleptics were most effective and ataractics least effective against ulcers produced by the method of Rossi.