Neovascularization can cause vision loss in proliferative diabetic retinopathy (PDR) and may be affected by many factors. Stromal cell-derived factor-1 (SDF-1) is a potent stimulator of angiogenesis. The study was aimed to investigate the expression of SDF-1 and its correlation with vascular endothelial growth factor (VEGF) in the eyes with diabetic retinopathy.The levels of SDF-1 and VEGF were measured by enzyme-linked immunosorbent assay in the vitreous of 41 eyes of 41 patients with PDR and 12 eyes of 12 patients with idiopathic macular hole (IMH). Vitreous fluid samples and fibrovascular preretinal membranes were obtained at vitrectomy. SDF-1 and VEGF were localized using immunohistochemistry.The vitreous concentration of VEGF was significantly higher in eyes with PDR ((2143.7 +/- 1685.21) pg/ml) than in eyes with IMH ((142.42 +/- 72.83) pg/ml, P < 0.001). The vitreous level of SDF-1 was also significantly higher in eyes with PDR ((306.37 +/- 134.25) pg/ml) than in eyes with IMH ((86.91 +/- 55.05) pg/ml, P < 0.001). The concentrations of both VEGF and SDF-1 were higher in eyes with active PDR than in eyes with inactive PDR. Panretinal photocoagulation (PRP) could decrease the SDF-1 levels in the vitreous of PDR patients. The vitreous concentration of SDF-1 correlated with that of VEGF in eyes with PDR (r = 0.61, P < 0.001). The costaining of SDF-1 and VEGF was confined to the vascular components in preretinal membranes.SDF-1 protein is highly expressed in both the vitreous and preretinal membranes of PDR patients; SDF-1 may be correlated with VEGF in angiogenesis in PDR.