Five cases of villous tumors of the duodenum are reported. These tumors have a predilection for the periampullary region and tend to present with jaundice or obstruction of the duodenal lumen. In four of these patients, malignant transformation was seen. Endoscopy and biopsy play a major rôle in attempting to obtain an accurate preoperative diagnosis. Unfortunately, the diagnosis of malignant degeneration is frequently missed, even when multiple biopsies are taken. For this reason villous tumors should always be resected, and the strategy of treatment must depend on pre-, intra- and postoperative histological evaluation, location in the duodenum and intra-operative findings.