A vitrectomy was performed in a diabetic patient because of unilateral vitreous hemorrhage, which persisted for six months. There was only background retinopathy in the other eye. In the operated eye, no proliferative retinopathy was found. During surgery a partial posterior vitreous detachment was noted with persistent vitreoretinal attachment to the superotemporal vascular arcade. Postoperative fundus examination and fluorescein angiography showed background retinopathy and the presence of a venous loop involving the superotemporal vein. Histologic description of venous loops with vitreoretinal adhesion was recently reported and it was suggested that this could lead to vitreous hemorrhage even in absence of severe proliferative retinopathy. To our knowledge, there is no previous report of diabetic vitreous hemorrhage probably due to a venous loop with vitreoretinal attachment.