The clinical course in 50 eyes was analysed after pars plana vitrectomy for progressive diabetic fibrovascular proliferations. Patients were assigned to pars plana vitrectomy if progression of proliferations occurred despite a photocoagulation treatment with a mean number of 3500 burns and additional peripheral cryoablation. All cases had visual impairment because of fibrovascular tissue covering the macula without detachment of the macula. Flat proliferations were present in all eyes without retinal elevation, vitreous detachment, or vitreous haemorrhage. The follow up intervals ranged from 13 months to 39 months (mean interval 24 months). Twelve months postoperatively, 36 eyes (72%) showed improved visual acuity, five eyes (10%) were worse, and nine eyes (18%) were unchanged. Thirty two eyes (64%) achieved a final visual acuity of 0.2 or better, and 45 eyes (90%) gained 0.05 or better. In only two eyes could reproliferation be observed. The postoperative course indicates that pars plana vitrectomy for diabetic fibrovascular proliferations covering the macula can preserve socially useful visual acuity of at least 0.05 in most cases.