Although hyperplastic polyps are generally believed to have no malignant potential, recent work has suggested that they might be more common in patients with adenomas. We evaluated whether hyperplastic polyps could serve as a marker for patients who might benefit from colonoscopy. We retrospectively reviewed 1,588 consecutive colonoscopy reports and hospital charts on 1,407 different patients examined between May 1983 and August 1985: 242 patients had adenomas, and 94 had hyperplastic polyps. Of patients with hyperplastic polyps 93.6% had concomitant adenomas, as compared with 35.7% of those without, p less than 0.001. Adenomas proximal to the rectosigmoid were found in 61.7% of patients with hyperplastic polyps and in 25.3% of those without, p less than 0.001. Patients with hyperplastic polyps in the rectosigmoid had proximal adenomas more frequently (64.7%) than did those without rectosigmoid hyperplastic polyps (29.4%), p less than 0.001. We conclude that patients with hyperplastic polyps are more likely to have adenomas, and patients with rectosigmoid hyperplastic polyps are more likely to have proximal adenomas. Based on these preliminary data, we believe that the finding of hyperplastic polyps in the rectosigmoid might justify full colonoscopy and that this should be studied further.