BACKGROUND: In Helicobacter pylori infection, the effect of short-term triple therapy with proton pump inhibitor plus two antibiotics on gastric ulcer healing is not well known. AIM: To compare 1-week triple therapy with 8-week proton pump inhibitor therapy on gastric ulcer healing in infected patients. PATIENTS AND METHODS: We randomly assigned 120 patients with H. pylori and gastric ulcers to proton pump inhibitor plus amoxicillin and clarithromycin for 1 week (n = 61) or proton pump inhibitor alone for 8 weeks (n = 59), with endoscopic assessment of ulcer healing 8 weeks after the start of treatment. RESULTS: Triple therapy eradicated H. pylori in 51 patients [intention-to-treat, 84%; 95% confidence interval (CI), 75-93%]. At 8 weeks, gastric ulcers were healed in 30 patients given triple therapy (49%; 95% CI, 37-62%) and in 49 patients given proton pump inhibitor (83%; 95% CI, 73-93%, P < 0.001). Healing rates in the triple therapy and proton pump inhibitor-only groups were 89% and 100%, respectively, for ulcers of < 1.0 cm in diameter, 54% and 77% for ulcers of 1.0 to < 1.5 cm in diameter, and 5% and 77% (P < 0.001) for ulcers of > or = 1.5 cm in diameter. CONCLUSIONS: One-week triple therapy healed most ulcers of < 1.0 cm, but not ulcers of > or = 1.5 cm. Short-term therapy is effective for gastric ulcers of < 1.0 cm, but, for larger ulcers, follow-up therapy to suppress acid is needed.