In a randomised clinical trial in 10 patients, the effects of a new anticholinergic, 8-isopropyl-3 alpha-DL-tropoyloxy-1 alpha H, 5 alpha H-tropanium hydroxide (ipratropiumbromide, active principle of Atrovent), on pentagastrin-stimulated gastric secretion was investigated. The study was performed in comparison to placebo, using the double-blind technique. Each patient served as his/her own control. As earlier test results seemed to indicate that ipratropium bromide had a particularly long duration of action, the special aim of the trial was to clarify whether an oral dose of 30 mg of the product inhibits gastric secretion for more than 11 h after administration. The findings show that basal acid secretion (BAO) was significantly reduced 11 ts following placebo. On the other hand, upon determination of maximum acid secretion (MAO) 12--13 h following administration, there was no difference between the anticholinergic and placebo. The results of the study of the study are discussed.