Two-hundred and forty-five eyes of 240 cases of branch retinal vein occlusion (BRVO) were analysed to determine the risk factors influencing the development of retinal neovascularization (NV).There were 208 eyes with major BRVO, 37 eyes with macular BRVO, 79 eyes with major BRVO developed NV, and the incidence of NV in this series was 37.9%.The incidence of vitreous hemorrhage in these eyes was 15.9%(39 eyes). The risk factors influencing the development of retinal NV in BRVO seem as follows: (]) the extent of retinal capillary nonperfusion area, (2)inefficiency of arterial infusion, (3) the extent of venous block at the arteriovenous crossing, (4) the duration of follow-up since onset of BRVO, and (5) the lack of collateral formation, Because BRVO has a long natural history, it is recommended that the patients should be followed-up for a long time If the vessels at peripheral retina closed, fluorescein angiography should be performed without hesitation and if the nonperfusion area is greater than 20-30 disc area, one should follow the patient carefully.As soon as the new vessels appear, laser photocoagulation should be applied without delay. （Chin J Ocul Fundus Dis,1994,10:67-70）