The study assessed excretion of nitrates in urine and saliva and that of nitrites with saliva of patients suffering gastric and duodenal ulcer. In both study groups, a positive correlation was established between nitrate concentration in saliva, on the one hand, and that in urine, and nitrite level in urine, on the other. The groups failed to show a difference in nitrate concentrations in either urine or saliva. Since retention of nitrates in the body of chronic gastritis patients held as precancer of the stomach proved no higher than that in patients with duodenal ulcer, the authors cast doubt on endogenous nitroso compounds as a cause of gastric cancer in cases of chronic gastritis.