Patients with severe sight threatening intermediate and posterior non-infectious uveitis frequently need systemic immunosuppressive therapy to maintain good vision. Research has shown that the autoaggressive cells involved in this disease are TH1 cells with high number of high affinity IL-2 receptors. Previous work in a non-human primate model for uveitis has shown that infusion therapy of an anti-Tac monoclonal antibody that has been humanized (i.e. HAT) had a salutory effect on the clinical expression of disease. The Tac portion of the IL-2 receptor is expressed during T cell activation. This pilot study has as an objective the evaluation of the potential efficacy of humanized anti-Tac monoclonal antibody therapy in the treatment of patients with endogenous sight-threatening uveitis. Patients 18 years and older who have non-infectious bilateral sight threatening intermediate and posterior uveitis are admitted. They need to be chronically taking at least 20 mg of prednisone or a combination of prednisone with any combination of systemically given cyclosporine or antimetabolites, and have demonstrated an intolerance to the regimen or desire to change. The therapeutic protocol calls for patients to be slowly weaned off their standard immunosuppressive regimen with the initiation of HAT infusions at a dose of 1 mg/kg every two weeks for the initial 12 weeks with longer intervals as the protocol continues. To date, eight patients have been entered into this pilot study with seven demonstrating good therapeutic results indicating that they are either off all of their standard medications or in the process of coming off, and have maintained good visual acuity with periodic infusions of HAT. The plan will be to recruit two more patients and to more fully evaluate the results. If the clinical results remain positive, we could envisage a phase II randomized study to fully define the potential efficacy of this therapy.