We analyzed the results of 105 diabetic vitrectomy cases. The vitrectomies were performed for progressive fibrovascular proliferation that caused epiretinal membranes, vitreopapillary traction, florid neovascularization, or subhyaloid hemorrhage, with or without substantial preoperative visual loss. Eyes with inactive retinal neovascularization, dense vitreous hemorrhage, traction retinal detachment involving the macula, or combined traction and rhegmatogenous retinal detachment were excluded. Seventy-four eyes (70%) had improved final vision. The final vision was unchanged in eight eyes (8%) and was worse in 23 eyes (22%). Factors associated with a favorable visual prognosis included the following: age of 40 years or less, preoperative visual acuity of 5/200 or better, absence of preoperative iris neovascularization, preoperative panretinal photocoagulation, and absence of an iatrogenic retinal break.