Objective To analyze the prognosis and results of residual membranes after vitrectomy for proliferative diabetic retinopathy (PDR).Methods It was a retrospective case series study.Five hundred and fifty eyes were diagnosed with phase Ⅴ or Ⅵ diabetic retinopathy and received vitrectomy and proliferative membrane peeling from Jan 2000 to June 2009.Among these patients,50 eyes of 43 patients had definite residual membranes,and were followed up for more than half a year.Their condition was summarized before,during,and after surgery,and the prognosis and results of the residual membranes were analyzed.Data were analyzed by Wilcoxon signed rank test and Mann-Whitney test.Results Location of the residual membrane: along the arterial arc-29 pieces (33％),inside the temporal arterial arc-4 pieces (5％),near the optic disk-7 pieces (8％),other locations-48 pieces (54％).Mean follow-up time was 27.7±26.2 months (6-102 months).Visual acuity improved in 42 eyes (84％),was unchanged in 1 eye (2％),and decreased in 7 eyes (14％).There were significant differences between preoperative and postoperative visual acuity (Z=-5.353,P＜0.01).The incidences of postoperative vitreous hemorrhage and retinal detachment were 14％(7/50) and 8％(4/50),respectively.There were recurrent proliferative membranes in 14 eyes,including 5 (6％,5/88) at the same location as the residual membranes.Most residual membranes (94％,83/88) manifested stability or atrophy.Conclusion Vitrectomy and membrane peeling for PDR is used to isolate the membrane and relieve retinal traction.Forced peeling is not suggested for focal membranes that adhere firmly to the retina.Residual membranes are not related to postoperative vitreous hemorrhage and retinal detachment.Most residual membranes can remain stable or become atrophied,and there is no significant relationship between residual membranes and recurrent proliferative membranes.