We describe life-threatening vasculitis of the small bowel following fulminant hepatitis. A 35-year-old man was admitted to our hospital due to consciousness disturbance and jaundice. He was diagnosed with fulminant hepatitis, and recovered after intensive medical care that included corticosteroid administration and artificial liver support. During reduction of the dosage of steroid, massive gastrointestinal hemorrhage occurred from the upper jejunum, revealed by arteriography. The hemorrhage could not be stopped, so a portion of the ileum, including the bleeding point, was excised. However, the intestinal hemorrhage continued from several small ulcers remaining outside the resected area. Pathological findings revealed an ulcerative region that was diagnosed as cytomegalovirus (CMV) vasculitis. His serum level of CMV (measured by real-time-detection polymerase chain reaction [PCR]) was high. Ganciclovir therapy was started, and manifestations of the CMV infection improved. In addition to CMV, PCR assay for hepatitis A virus (HAV), HBV, HCV, Epstein-Barr virus (EBV), human herpes virus-6 (HHV-6), and herpes simplex virus (HSV) was performed, but no viruses other than CMV were detected. We are the first to report such a case. We conclude that the possibility of CMV enteritis should be considered when patients present with unexplained fever and gastrointestinal hemorrhage following fulminant hepatitis, and we conclude that the early administration of ganciclovir should be considered.