A 43-year-old man presented with gastrointestinal bleeding. A tumor with central ulceration was observed in the jejunum, with the use of a new enteroscopy system called "double-balloon enteroscopy". Bleeding after biopsy sampling of the tumor was controlled endoscopically by using electrocoagulation. Histological findings of the biopsy specimens were consistent with gastrointestinal stromal tumor, and this was surgically resected. Double-balloon enteroscopy was useful for the diagnosis as well as the control of bleeding in this patient.