Picartamide had potent antisecretory and antiulcerogenic effects which were, at least, 10 times more pronounced than those of cimetidine. The mechanism of action of picartamide has not yet been determined but it seems that an anticholinergic or an H2 receptor antagonist effect should be excluded. The results show that picartamide is also active on the pure vagus-stimulated gastric acid secretion. The lack of effect upon gastric pepsin and plasma PP suggests that picartamide is not likely to act on the basolateral cholinergic receptor and that it affects further cellular steps involved in hydrogen ion secretion.