The gastric anti-ulcer activity of (+)-cyanidanol-3, a specific histidine decarboxylase inhibitor was studied on various types of experimentally induced ulcers in rats viz., pylorus-ligated and restraint ulcers, gastric mucosal damage induced by non-steroid anti-inflammatory drugs like aspirin, phenylbutazone, indomethacin and ibuprofen and by reserpine. Guinea pigs subjected to histaminee challenge were also used in the study. (+)-Cyanidanol-3 possesses significant gastric anti-ulcer activity in all these models. However, the ED50 values against pylorus-ligated and restraint ulcers and against histamine-induced ulcers in guinea pigs differed significantly from one another. It was most effective against the restraint ulcers in rats. It is suggested that mechanisms involving formation, release or direct antagonism of histamine may be involved in the protective effects of (+)-cyanidanol-3 observed in this study. As its use as an antihepatotoxic drug has already been established, it is worthwhile to consider it for clinical trials in the therapy of human stress ulcers.