The present study investigated both the healing rate (after four weeks) and the relapse rate (during six months) following treatment with the dopamine-like drugs bromocriptine (2.5 mg twice daily), amantadine (100 mg nocte), or with the H2 blockers cimetidine (800 mg nocte), and famotidine (40 mg nocte) in 124 patients with endoscopically proven duodenal ulcer (DU). The ulcer was completely healed in 27 (amantadine), 26 (bromocriptine), 23 (cimetidine), and in 24 (famotidine) patients. Relapse was noted in 34.7% (cimetidine) and 25% (famotidine) versus 11.7% (amantadine) and 7.7% (bromocriptine) DU patients. No significant difference was found in initial healing rates. However, the relapse rate in the cimetidine-treated group was significantly higher than in all the other test groups. Additional comparisons between all the treatment categories showed a significantly lower relapse rate with the dopamine-like agents. These important new results indicate that dopamine-like compounds are equally effective as H2 blockers in inducing DU healing and may offer a promising advantage over H2 blockers concerning their efficacy in preventing ulcer relapse in DU patients.