With the advent of fiberoptic endoscopy and modern radiographic techniques, the majority of detected polyps are less than 1 cm. During a seven-month period, we studied 140 patients who had radiographically demonstrated colonic polyps that were confirmed by pathologic study. Tissue specimens were obtained by proctoscopy, colonoscopy, or surgery. There were 222 polyps of which 144 (65%) were 1 cm or less in size, with the preponderance (80%) of these being adenomatous. Of the 82 polyps that ranged in size from 6-10 mm, 68 (83%) were adenomas, including one carcinoma and five villous adenomas. Forty-seven (72%) of the diminutive polyps (less than or equal to 5 mm) were adenomatous, including two with atypia. Our results correspond to those of several recent endoscopic studies, reporting that a small colonic polyp is most likely to be adenomatous, and that it possesses the potential for growth and malignant transformation. The detection of small polyps during barium enema examination is thus warranted, particularly in the proximal colon where the majority are adenomatous. The clinical management of polyps is becoming more aggressive, and the removal of even small lesions (less than or equal to 5 mm) is now performed if they are found incidentally during colonoscopy.