Five patients with villous adenomas in the duodenum are described. In one patient malignant degeneration had occurred at the time of diagnosis. This patient was treated with a pancreaticoduodenal resection and is doing well 2 years postoperatively. The other four patients all had a duodenotomy and a local excision of the tumour. One patient had a recurrence with malignant degeneration within 1 year. The other three patients are doing well without signs of recurrence 1-4 years postoperatively. It is concluded that duodenal villous adenomas are potentially malignant. The strategy of surgical treatment is discussed.