We define “giant” gastric ulcer as a chronic gastric ulcer, with a diameter ≥ 3 cm. Treatment of inpatients with several conventional antiulcer agents resulted in significantly lower healing rates in giant gastric ulcer than in “large” (15 < &thetas; 30 mm) or “medium” (5 < &thetas; ≤ 15 mm) ulcers. In 48 patients with giant gastric ulcers treated with ranitidine, cumulative endoscopic healing rates were: 0% after 2 weeks, 16.7% after 4 weeks, 50.0% after 6 weeks, 77.1% after 8 weeks, 85.4% after 10 weeks, and 87.5% after 12 weeks of treatment. Corresponding healing rates were determined for the control group, which included patients treated with various conventional antiulcer agents. Comparison of these results revealed that from the fourth week of treatment onward, healing rates of the ranitidine group were significantly higher than those of the control group. There was little difference in the cumulative healing rates in the ranitidine group. From these results, ranitidine is considered to be useful in the treatment of giant gastric ulcer.