Hydrogen clearance was used to assess blood flow in fundal and antral gastric mucosa as well as in the lobule of the auricle in 127 patients with ulcer (99 duodenal and 28 gastric ulcer cases), 34 patients with gastric, duodenal, pancreatic and biliary nonulcer lesions against 20 healthy subjects. The findings underwent analysis in relation to the disease form and phase, baseline characteristics of the mucosa (morphological, functional and bacteriological) and changes in them in response to pentagastrin (6-mu-g/kg), alupent (0.0075 mg/kg), clofelin (0.0015 mg/kg) administration. For ulcer involving the body of the stomach and sutured perforated duodenal ulcer, fundal and antral mucosa blood flow showed a decrease by 1/3, the lowest values presenting in the active disease phase. Diminution in gastric mucosa blood flow correlated with gravity of its gastritic lesion and was not directly related to its Campilobacter contamination. Pentagastrin stimulated blood flow in fundic mucosa and led to its 30 % increase whereas the flow intensity remained unaffected in the antral mucosa and skin (lobule of the auricle). Acid production in response to pentagastrin introduction rose 3.5-fold, pepsin 2.1-fold. Alupent and clofelin do not affect blood flow causing a 30-50 % increase and decrease in acid and pepsin production, respectively. Separate neurohumoral regulation of gastric mucosa blood flow and secretory activity of the latter permits differential correction of each of the impaired functions.