Eighty-two patients with colon and rectal polyps containing invasive adenocarcinoma treated by polypectomy alone were studied. Seven of 34 patients (21 percent) with sessile lesions had an adverse outcome, including five local recurrences and two distant metastases. They occurred from 4 to 68 months after the polypectomy. Forty-seven pedunculated polyps with invasion to the head (Level 1) or to the stalk (Level 3) and one polyp to the base of the stalk (Level 4) had no evidence of local recurrence or signs of metastasis. Twenty-eight percent of patients were found to have adenomatous polyps, and 4 percent had malignant polyps during the follow-up examinations (range, 3-119 months; mean, 53 months). The findings suggested that pedunculated polyps with invasion to the head (Level 1), neck (Level 2), or stalk (Level 3) can be safely treated with a complete polypectomy provided that the carcinoma is not undifferentiated. Sessile lesions as well as Level 4 pedunculated lesions should be treated aggressively. If resection is not performed, a long-term follow-up in these patients is essential.