To evaluate the surgical indications and results among patients undergoing pars plana vitrectomy for complications of diabetic retinopathy, the clinical records of all such patients treated by a single surgeon from January 1992 through August 1996 were reviewed. Pre- and postoperative visual acuity, indications for surgery, surgical methods, and anatomic outcomes were recorded and analyzed. A total of 106 eyes (92 patients) were included. Surgical indications included nonclearing vitreous hemorrhage (21 eyes), active fibrovascular proliferation (28 eyes), traction retinal detachment (42 eyes), premacular hemorrhages (3 eyes), combined traction and rhegmatogenous retinal detachment (7 eyes), severe macular edema (1 eye), and progressive macular or disc traction (4 eyes). Surgical techniques ranged from tissue segmentation to combined delamination and segmentation. Anatomical success was obtained in 90 eyes (84.9%). Visual acuity improved in 69 eyes (68.0%), stabilized in eight eyes (7.5%), and decreased in 29 eyes (28%). All 21 eyes with vitreous hemorrhage had anatomical success, while 10 of 42 (24%) eyes with traction retinal detachment eventually had retinal detachment. Fourteen eyes had postoperative persistent or recurrent vitreous hemorrhage requiring air-fluid exchange or vitreous lavage. Silicone oil was used in eight eyes. Surgical failure was mainly caused by iatrogenic breaks with persistent traction, or severe anterior or posterior reproliferation. These findings indicate that reasonably successful anatomical outcomes can be achieved with modern surgical methods. However, improvements in visual acuity may be less satisfactory. Eyes with widespread, thickened fibrovascular complexes with active neovascularization, and extensive traction retinal detachment have a poor prognosis.