Fourteen patients with primary malignant duodenal tumors are studied. Twelve patients had adenocarcinomas and two patients had malignant lymphomas. Preoperative diagnostic procedures, such as radiographic study of duodenum with hypotonic duodenography, complete duodenoscopy with biopsy and artertiographic studies are discussed. Early diagnosis is the key for curative surgical treatment since these tumors seem to disseminate rather late. In patients with primary duodenal carcinoma the resectability rate was 66.7%—seven Whipple resections and one segmental resection. Only one patient in our series died after a Whipple resection. There was no mortality after other procedures. The five year survival rate was 14.2%. There is a definite correlation between regional lymph node involvement and survival time. The mean survival period after Whipple resection without lymph node invasion is 56.5 months in our series. The survival period after Whipple resection for adenocarcinoma with regional lymph node invasion (6 months) is identical to the survival after palliative internal derivations for duodenal adenocarcinoma (5.8 months). It is concluded that a positive peroperative frozen section of a regional lymph node should exclude resective procedures (except in patients who hemorrhage) because they have a higher mortality rate as derivative procedures. Fifty per cent of the patients treated for malignant duodenal lymphoma is tumor free two years after a radical surgical therapy combined with chemotherapeutical treatment from the early postoperative period.