Colloidal bismuth subcitrate (CBS) in the form of a chewable tablet has been compared with ranitidine in the short-term treatment of benign gastric ulcers. Eighty patients were admitted to this randomised single blind study. Endoscopic control was carried out after 4 weeks, and after 8 weeks when healing was incomplete or had not occurred at the 4-week examination. After 1 month of therapy the healing rates were 70% with CBS and 62.5% with ranitidine (P = not significant). At two months the corresponding cure rates were 87.5% and 79%, respectively (P = not significant). Antacid consumption was higher in the group treated with ranitidine, but the difference was not statistically significant. Patient cooperation was good and similar in the two groups. These findings confirm that CBS, in tablet form, is at least as effective as ranitidine in the acute treatment of benign gastric ulcers.