The purpose of this study was to simultaneously measure the concentrations of multiple cytokines, including vascular endothelial growth factor, in the vitreous of patients with diabetic retinopathy and to examine their relation with clinical findings. Vitreous samples from 46 eyes with diabetic retinopathy and 19 eyes with nondiabetic macular disease (controls) were used. Nine cytokines were simultaneously measured using a FACSCalibur flow cytometer. Vascular endothelial growth factor, interleukin-8, monocyte chemotactic protein-1, interferon-inducible protein-10, and monokine induced by interferon-gamma were detected in the vitreous samples, and the concentrations were significantly (P < 0.001) higher in patients with diabetic retinopathy compared with control subjects. Vascular endothelial growth factor, interleukin-8, monocyte chemotactic protein-1, and monokine induced by interferon-gamma concentrations were significantly (P < 0.05) higher in active retinopathy than in inactive retinopathy. Furthermore, a significant (P < 0.01) positive correlation was observed between vascular endothelial growth factor concentration and interleukin-8, monocyte chemotactic protein-1, interferon-inducible protein-10, or monokine induced by interferon-gamma concentration in the vitreous. Vascular endothelial growth factor, interleukin-8, monocyte chemotactic protein-1, interferon-inducible protein-10, and monokine induced by interferon-gamma were expressed at high levels locally in ocular tissues in diabetic retinopathy, and these cytokines may form a network and interact to impact the pathogenesis of the disease.