This study investigated the effect of colloidal bismuth subcitrate and cimetidine on Campylobacter pylori in peptic disease. In 74% of 135 patients with peptic disease diagnosed at endoscopy C pylori was detected before treatment. Compared with cimetidine, colloidal bismuth subcitrate significantly decreased the incidence of C pylori after six weeks of treatment (p less than 0.001). In the colloidal bismuth subcitrate group, subsequent healing of the lesion was correlated with the clearance of C pylori, unlike in the cimetidine group. C pylori was strongly associated with the presence of histological gastritis, which was decreased by colloidal bismuth subcitrate (p less than 0.001).