Records of 32 patients with 34 villous and tubulovillous adenomas of the duodenum, treated at the Cleveland Clinic over the past 21 years, were reviewed. Twenty-two patients (69%) had complete resection of the adenoma; the incidence of malignancy was 47%. Five patients underwent a Whipple procedure; 4 patients had segmental resection of the duodenum; 12 had wide local excision of the adenoma; 1 had both a segmental resection and a local excision for two separate adenomas; and 5 patients had endoscopic excision alone. The remaining five patients underwent exploratory laparotomy alone or with palliative bypass procedures. A 28% recurrence rate was observed, all of these after segmental resection, local excision, or endoscopic excision. The highest recurrence rate was associated with local excision. The 2- and 5-year survival rates for patients with adenomas containing invasive cancer were 22% and 0%, respectively, compared to 87% and 87%, respectively, for benign adenomas (including those with carcinoma in situ). Twenty-two per cent of patients had intestinal polyposis syndromes. Duodenal adenomas were diagnosed a mean of 17 years after colectomy for polyposis, indicating the need for continued surveillance in these patients.