The results and complications of pars plana vitrectomy for nondiabetic vitreous hemorrhage due to retinal and choroidal vascular disorders were studied in 68 eyes of 66 patients. Diagnoses included: retinal branch vein obstruction (34 eyes), choroidal neovascularization (15 eyes), central retinal vein occlusion (5 eyes), Eales' disease (10 eyes), pars planitis (3 eyes), and hemoglobin S-C retinopathy (1 eye). The duration of the vitreous hemorrhage was 6 months or more in 48 eyes (71%), and averaged 17.8 months. Preoperative visual acuity was less than 5/200 in 57 eyes (84%). Best postoperative visual acuity was 5/200 or better in 55 patients (81%), and vision improved two or more lines after vitrectomy in 54 eyes (80%). Patients with retinal branch vein obstruction, Eales' disease, or pars planitis had the best prognosis. Those with central retinal vein obstruction or choroidal neovascularization had the worst prognosis.