We analyzed the surgical results for 197 eyes that underwent vitrectomy for diabetic traction detachment of the macula. The retina was successfully reattached in 130 of the 197 cases (66%), although the final level of vision depended on the amount of permanent macular damage from the previous detachment and on the effects of the retinal vascular disease. At the final examinations, 112 eyes (57%) had improved visual acuities, 68 eyes (35%) were worse, and 17 eyes (9%) were unchanged. Thirteen eyes (7%) had final visual acuities of 20/40 or better, 103 eyes (52%) had final visual acuities of 20/50 to 20/800, and 81 eyes (41%) had final visual acuities worse than 20/800. Two preoperative factors were associated with a worse prognosis for achieving a final visual acuity of 20/800 or better: preoperative vitreous hemorrhage (P less than .01) and the absence of preoperative scatter retinal photocoagulation (P less than .01). Additionally, two surgical factors, lens removal and the creation of iatrogenic retinal breaks, were associated with a poorer visual prognosis (P less than .002 and P less than .01, respectively). The group of eyes that underwent lens removal during vitrectomy also had a significantly higher incidence of postoperative iris neovascularization compared to eyes in which the lenses were not removed (P less than .05).