Pharmacokinetics and gastric secretion suppressing properties of a new drug, trithiozine (TR 4-(3,4,5-trimethoxybenzoyl)tetrahydro-4, 4-oxazine), were studied in man. Its availability, if taken orally, is prompt and very good; its blood plasma level lasts for > 5 h. In basal conditions volume of gastric juice is suppressed by TR as it is by propantheline bromide (PPB). In contradistinction of PPB, TR reduces basal acid output. After histamine stimulation TR is not as effective as PPB in reducing both volume and acid output. TR did not appear to affect the plasma gastrin level. Lack of typical anticholinergic side effects i.e., mouth dryness, vision blurring, etc., and antisecretory activity limited to basal conditions on the other offer a new modification of the old approach to therapy of gastroduodenal ulcer. Clinical trials seem justified.