Background: An association between Helicobacter pylori infection and lymphocytic gastritis has been postulated. Aim: To assess the long-term effect of H. pylori eradication therapy on lymphocytic gastritis in a double-blind, placebo-controlled, multicentre trial. Methods: Patients with lymphocytic gastritis were randomized to receive either 1-week triple therapy for eradication of H. pylori or omeprazole plus placebo. Endoscopy and histology was performed at baseline and after 3 and 12 months. Patients of the omeprazole/placebo group with persistent lymphocytic gastritis after 12 months received crossover open-label triple therapy. Results: Fifty-one patients were randomized. Intention-to-treat analysis revealed a trend to a higher healing rate of lymphocytic gastritis 3 months after triple therapy compared with omeprazole/placebo (83.3% vs. 57.7%, 95% CI for RR: 0.8-2.8, P = 0.06). After 12 months, the healing rate of lymphocytic gastritis was significantly higher after triple therapy compared with omeprazole/placebo (intention-to-treat 95.8% vs. 53.8%, 95% CI for RR: 1.1-3.5, P = 0.01). All patients (n = 5) who received crossover triple therapy, showed healing of lymphocytic gastritis after further 12 months. Conclusion: Our study demonstrates that 1-week triple therapy aiming at eradication of H. pylori leads to a complete and long-lasting resolution of lymphocytic gastritis in the majority of patients.