To evaluate the effectiveness of vitrectomy on eyes with proliferative diabetic retinopathy (PDR). · METHODS: A total of 139 eyes of 93 cases with PDR underwent vitrectomy and were followed up for 3-24 months (16.72±8.53 months; mean±SD). The visual acuity and the factors causing recurrence of operation were analyzed. · RESULTS: The visual acuity was improved in 98 eyes (70.50%) after vitrectomy. The mean postoperative visual acuity was significantly better than the mean preoperative visual acuity. The main reasons for the failure of operation were retinal detachment and maculopathy. · CONCLUSION: These results demonstrate that vitrectomy is generally an effective procedure in treating PDR