Forty-six consecutive patients with chronic renal failure (CRF) were assessed radiographically, endoscopically and histologically for duodenal inflammation. Their gastric secretion was also examined. Thirty-eight patients with non-ulcer dyspepsia served as controls. Histologically established duodenitis was more common in CRF patients than in controls. Among the non-dialyzed patients its prevalence reached 28% (9/32), while in the controls it was 5% (2/38) (p less than 0.05). The CRF patients with duodenitis had upper GI symptoms, hypersecretion of acid (p less than 0.05) and duodenal ulcer disease (p less than 0.05) more frequently compared with the CRF subjects with normal duodenal mucosa. The correlation of radiographically and endoscopically detected duodenitis with that found microscopically was poor.