To identify the cellular source and mechanism of the diabetes-induced upregulation of IL-1β in the retina we studied the effect of high glucose and IL-1β itself on the expression of the cytokine in microglial, macroglial, and retinal vascular endothelial cells; and the effect of diabetes on the expression of IL-1β in isolated retinal vessels and on the temporal pattern of IL-1β upregulation and glial reactivity in the retina of streptozotocin-diabetic rats. The gene discussed is IL1B; the disease is diabetes mellitus.