A double-blind, placebo-controlled trial was performed, using 400-mg cimetidine tablets or placebo twice daily for 4 weeks in 100 patients with non-ulcer dyspepsia (NUD) and erosive prepyloric changes (EPC) grade 2 or 3. Symptomatic assessment was made weekly and endoscopic assessment on completion of the treatment period. Symptomatically, a significant effect of cimetidine versus placebo on epigastric pain/discomfort was recorded after 2 weeks' treatment (p less than 0.05). Endoscopically, there was a significant improvement, according to our grading scale of EPC, in the cimetidine-treated group, as compared to the placebo-treated group (p less than 0.05). On the basis of our findings, patients with NUD and EPC who have epigastric pain/discomfort as a prominent symptom seem to profit from treatment with cimetidine.