This work was aimed to study clinical features of H. pylori-associated duodenal ulcer (DU) and elucidate morphological features of gastric mucosa (GM) in patients with bronchial asthma (BA). Simultaneous prospective examination of 118 patients aged 18-64 yr included clinical and endoscopic study of the gastroduodenal region with the assessment of gastroenterological symptoms and morphological analysis of GM and duodenal biopsies by histological, histochemical, and morphometric methods. It was shown that GM inflammation in patients with DU and BA is associated not only with H. pylori infection but also with the phase of BA. Structural changes of GM in the patients with DU and BA, unlike those with DU without BA, were apparent not only in the antrum but also in the fundus. Growing density of eosinophil, neutrophil and mast cell infiltration of fundal and antral GM as well as increased total number of cells in the antrum reflects active immune-mediated inflammation in GM lamina propria. It is concluded that negative effect of uncontrolled BA on the clinical course of DU is not restricted to the association of DU exacerbation with the absence of BA control; it is also responsible for enhanced activity of gastritis. One of the possible factors determining combination of H. pylori-associated duodenal ulcer with BA is chronic hyperergic inflammation and marked structural changes in GM.