Hyperplastic polyps seen at sigmoidoscopy are markers for additional adenomas seen at colonoscopy. Asymptomatic individuals undergoing screening flexible sigmoidoscopy were prospectively studied. Polyps were found in 185 subjects. The endoscopist recorded an opinion on the polyps' histology based on endoscopic appearance. No polyps were removed at sigmoidoscopy. All subjects with rectosigmoid polyps then underwent colonoscopy and polypectomy. Of them, 99 subjects (54%) had at least one rectosigmoid adenoma, 69 (37%) had only hyperplastic polyps, and 17 (9%) had other findings. The endoscopists' opinion of the histopathology of polyps at sigmoidoscopy was correct for 61% of the lesions. Of subjects with adenomatous rectosigmoid polyps, 29% had additional adenomas at more proximal sites. Proximal adenomas were found in 28% of patients with hyperplastic rectosigmoid polyps. Patients with rectosigmoid hyperplastic polyps had the same risk for additional proximal adenomas as patients with rectosigmoid adenomatous polyps. 