Background and Aims: Recent advances in enteroscopy facilitate detection and treatment of the small intestinal vascular lesions which are major causes of obscure gastrointestinal bleeding (OGIB). The purpose of this study was to evaluate the clinical characteristics of such lesions and efficacy of treatment. Methods: Between December 2003 and July 2008, 233 cases with OGIB were examined by double-balloon or single-balloon enteroscopy. Enteroscopy was performed twice with antegrade and retrograde approaches to evaluate the entire small intestine. We classified endoscopic appearance of the small intestinal vascular lesions into the following 6 types according to the Yano-Yamamoto classification (Gastrointest Endosc 2008;67: 169-72): type 1a, punctulate erythema (less than 1mm); type 1b, patchy erythema (a few mm); type 2a punctulate lesions (less than 1mm) with pulsatile bleeding; type 2b, pulsatile red protrusion without surrounding venous dilatation; type 3, pulsatile red protrusion with surrounding venous dilatation; type 4, other lesions not classified into any of the above categories. Results: Among 233 OGIB cases, 31 (13%) cases with small intestinal vascular lesions were found. Their mean age was 57 ± 7.8 years old, and 12 were men and 19 women. Of the 31 cases, 13 (42%) patients had liver diseases (chronic hepatitis 3, liver cirrhosis 10), 5 (16%) renal diseases (chronic kidney disease 1, renal failure 4), 4 (13%) heart diseases (ischemic 2, chronic heart failure2), and 6 (19%) diabetes mellitus. Locations of the vascular lesions were more frequent in the distal small intestine; 18 in the ileum, 6 in the both ileum and jejunum, 7 in the jejunum, and one in the duodenum. Endoscopic appearance revealed that 8 cases were diagnosed as being type 1a, 19 type 1b, 1 type 2a, 2 type 2b, 1 type 3. Regarding therapy, we performed endoscopic treatments in 26 cases (argon plasma coagulation in 8, heat probe in 17, and clipping in one), surgical resection in 2 cases, and preserving therapy in 3 cases. Although 24 cases with endoscopic therapy resulted in the complete hemostasis except 2 cases with multiple angioectasia, we experienced re-bleeding in 9 (29%) cases during the follow-up (mean period was 56 months). In such cases, 7 (78%) of the 9 cases had multiple vascular lesions in the small intestine. Conclusions: Small intestinal vascular lesions were found in 31 (13%) of OGIB cases and they were frequently located in the distal small intestine and type 1b was most common. Patients with small intestinal vascular lesions often have severe underling diseases. Higher re-bleeding rate suggest that strict follow-up is needed even after successful treatment.