The new H2 receptor antagonist, famotidine, has been tested in open and double-blind studies in over 2,000 acute duodenal or gastric ulcer patients as well as in the maintenance of chronic duodenal ulcer patients. In early studies, dosages of 20 mg b.i.d. were found to achieve better results than 10 mg b.i.d. and equivalent to 20 mg t.i.d. Trials comparing famotidine to cimetidine, ranitidine, and gefarnate found the new agent to be approximately equivalent to cimetidine and ranitidine and superior to gefarnate in the treatment of acute duodenal ulcer. Similar trials were conducted to compare different types of therapy in acute gastric ulcer. Famotidine 40 mg at bedtime was significantly more effective than placebo, and a 20 mg b.i.d. dosage once again proved at least as active as cimetidine 200 mg q.i.d. and considerably more effective than gefarnate. Furthermore, famotidine 20 mg at bedtime was found to effectively prevent relapses for at least 6 months. The side effect profile was extremely favorable – adverse reactions were rare and never positively associated with the drug. Although experience with this new agent is still somewhat limited, preliminary results indicate that famotidine is at least comparable with the other available H2 antagonists and can be considered an excellent choice for treatment of peptic ulcer disease.