37 patients with epigastric pain and chronic erosive gastritis underwent an open controlled therapeutic trial with bismuthsubsalicylate (BS). Group A (21 patients) was treated with BS, liquid, 4 X 314 mg for three weeks, group B (16 patients) with BS tablets, 3 X 300 mg for two weeks. A significant reduction of symptoms (p less than 0.001) and endoscopically assessed chronic erosions (p less than 0.001) was achieved in both groups. Campylobacter pylori was detected in 89% of the patients before treatment, but was absent in 78% of the patients after treatment. The histological grading of antral mucosa showed a significant reduction (p less than 0.001) of polymorphonuclear cell (PML) infiltration after two and three weeks treatment respectively. While in group A PML cells had disappeared from gastric mucosa in all but two patients, in group B 50% of the patients had some degree of PML cell infiltration left in the antral mucosa. This study confirms the beneficial effect of BS in the treatment of C. pylori associated active chronic gastritis and reemphasizes the pathogenetic role of C. pylori in this disease.