Duodenoscopy in celiac disease has identified several markers of the disease. Our aim was to evaluate, in a prospective study, the usefulness of the different endoscopic features in 100 consecutive cases referred to endoscopy for intestinal biopsy. Histological examination of duodenal samples showed severe villous atrophy (grade III/IV) in 36 patients. Of these patients, 34 had endoscopic markers suggestive of celiac disease. These were reduction in number or loss of Kerkring's folds (in 27), mosaic pattern (14), scalloped folds (12), and visibility of the underlying blood vessels (5). Endoscopic visualization of these markers had a sensitivity of 94%, a specificity of 92%, and a positive predictive value of 84%. Reduction in number, or loss of, Kerkring's folds was the most sensitive (76%) and specific (98%) single endoscopic change indicating celiac disease. Duodenoscopy permitted diagnosis in three of four asymptomatic patients in a group of 24 first-degree relatives of celiac disease patients. We conclude that endoscopy of distal duodenum is a sensitive and specific indicator of celiac disease.