Reported are the autopsy findings of a 55-year-old man who died unexpectedly 20 h after a subtotal gastrectomy of an early gastric cancer. The cause of his death was a superior mesenteric venous thrombosis, involving his small bowel which manifested a marked vascular engorgement. The entire small bowel mesentery was thickened and edematous, and hemorrhagic infarctions were scattered near the bowel. Many fresh thrombi could be identified in the superior mesenteric veins. This case is described, together with the legal aspects of medical malpractice.