Posterior uveitis is thought to be a T-cell mediated disease since active foci of inflammation, identified in eyes enucleated for the complications of intraocular inflammation, are found to be predominantly composed of CD4+ T-cells. Few B-cells and little immunoglobulin are found suggesting that antibody and immune complex deposition do not play a major role in perpetuating the inflammatory process. As ocular biopsy is not a feasible method for monitoring disease activity and response to treatment, parameters of T-cell activation and retinal damage have been studied in the peripheral blood. These have included antibody and T-cell sensitisation to retinal S-antigen, serum soluble IL-2 receptors and IL-2 receptors on activated T-cells. None of these parameters, however, have been found to be useful in the monitoring of ocular disease activity alone or in the prediction of disease relapse.