To investigate the effect of follow-up study after colorectal polypectomy, 156 patients with symptomatic stalked adenomas with light to severe dysplasia were allocated at random to colorectal examination every 6 (A) and 24 (B) months after colonoscopic polypectomy. No high-risk group could be identified. Twenty-one of the 23 new polyps were located above the rectum, but 15 could have been removed during examination with the flexible sigmoidoscope. The risk of new adenomas was similar at all 6-month examinations, during the first 4 years of the study. A small carcinoma (Dukes A) was found at 24 months in group B. A fatal colonic perforation was seen in group A after seven previous colonoscopies without complications. The new polyps caused no symptoms other than minimal bleeding in some of the patients, and because increasing the rate of colonoscopies increases risk of complications, it was considered justified to prolong the intervals to 24 and 48 months, at random.