We determined whether interleukin-8, monocyte chemotactic protein-1, and macrophage-colony stimulating factor are present in the vitreous of patients with proliferative diabetic retinopathy (PDR) or proliferative vitreoretinopathy (PVR). The levels of these cytokines were measured by specific enzyme-linked immunoassays in vitreous from 30 patients with PDR, 13 patients with PVR, and 26 control individuals, including 10 cadaver eyes and 16 patients with idiopathic macular holes, idiopathic macular puckers, vitreous hemorrhages, or uncomplicated retinal detachments. Detectable levels of interleukin-8 were found in 90% of vitreous samples of patients with PDR, 85% with PVR, and 58% of control samples. IL-8 was significantly increased in PDR (mean +/- SEM; 25.0 +/- 5.3 ng/ml; p = 0.01), but not in PVR (11.9 +/- 3.9 ng/ml; p = 0.50) compared to control human vitreous (8.5 +/- 2.5 2.5 ng/ml). MCP-1 was detected in 90% of vitreous samples of patients with PDR, 92% with PVR, and 81% of control samples. MCP-1 was significantly increased in PDR (6.2 +/- 0.9 ng/ml, p = 0.001) and PVR (7.7 +/- 2.5 ng/ml, p = 0.001) over the levels in control vitreous (1.2 +/- 0.2 ng/ml). M-CSF was detected in 94% of vitreous samples of patients with PDR, 88% with PVR, and 92% from control vitreous. M-CSF was significantly elevated in PDR (32.3 +/- 8.3 ng/ml, p = 0.03), but not in PVR (23.6 +/- 12.8 ng/ml, p = 0.4) compared to control (10.7 +/- 3.5 ng/ml). Our results suggest that IL-8, MCP-1, and M-CSF participate in the pathogenesis of PDR and PVR.