The therapeutic effects of panretinal cryotherapy(PRC)on proliferative diabetic retinopathy(PDR)were prospectively investigated in 80 eyes with PDR of 44 patients.Forty eyes with PDR(20 of them stage Ⅳ and 20 stage Ⅴ)received PRC operation.Of the 80 eyes,the other 40 ones with stage Ⅳ and Ⅴ similar to the formers were observed conservatively as controls.The follow up duration was 2 years.We found that in the cases of stage Ⅳ,no more remarkable visual loss was found after operation.There was a significant difference comparing with the control（P＜0.002）,and the retinal neovascularization regressed more noticeably than the control group（P＜0.001）.In the cases of stage Ⅴ,the incidence of the traction retinal detachment was 55% in the operated group,and was 20% in the control group.There was a statistic difference between them（P＜0.05）.The clearance of the vitreous hemorrhage was more rapid in the operated group than the control（P＜0.025）.The above results suggest that cryotherapy is suitable for the cases of earlier stage which cannot be performed with photocoagulation for any reasons,but not for the patients with advanced retinal proliferation.Photocoagulation for any reasons,but not for the patients with advanced retinal proliferation. （Chin J Ocul Fundus Dis,1993,9:148-151）