Ten double-blind randomized studies with omeprazole versus ranitidine in duodenal ulcer healing have been published. The total number of patients in the trials amounted to 2225. To detect treatment differences, a meta-analysis was performed. After 2 and 4 weeks of treatment results have been evaluated. After 2 weeks of treatment omeprazole produced higher healing rates than ranitidine in nine studies. However, at 4 weeks numerical differences in favour of omeprazole were found in nine studies. Relief of ulcer symptoms occurred more rapidly with omeprazole than ranitidine. No major clinical or biochemical side effects were recorded. However, no data are available about maintenance therapy in double-blind randomized studies comparing both drugs or about rebleeding rates in bleeding duodenal ulcer treatment.