Although metastases from primary carcinoma of the lung to the small intestine appear to be more common than previously suspected, they rarely produce symptoms. Such metastases may present as bowel perforations. Overt gastrointestinal bleeding has been described only as a prelude to perforation. We describe the case of a 55-yr-old man with carcinoma of the lung that had metastasized to the brain and to the third part of the duodenum. The duodenal metastasis presented with massive upper gastrointestinal hemorrhage. The metastasis was seen to be actively bleeding at endoscopy, and a direct fistula from a branch of the superior mesenteric artery to the third part of the duodenum was shown angiographically. Arterial invasion and destruction by tumor was confirmed at postmortem examination. This complication of metastatic carcinoma of the lung has not been previously described in the English literature.