The efficacy of omeprazole 20 mg a day was assessed against ranitidine 150 mg twice a day in the healing and relapse of duodenal ulcer. Forty three endoscopically verified cases were allocated to 2 weeks of treatment, which was extended to 4 weeks, if the ulcer persisted on day 15. Two cases were excluded due to deviation from the protocol. Of 41 evaluable cases, 21 received omeprazole and 20 ranitidine. Healing rates with omeprazole and ranitidine at 2 weeks were 71% and 70% respectively which rose to 100% and 90% at 4 weeks (N.S). There was no significant difference in pain relief in two groups. Follow-up endoscopies, in 33 healed cases revealed 100% relapse at 3 months in omeprazole and 79% in ranitidine treated cases (P < 0.05).