Pars planitis remains a difficult and perplexing clinical entity. Sequelae of long-standing disease include cataract formation, cystoid macular edema, epiretinal membrane formation, neovascularization, vitreous hemorrhage, and retinal detachment. In addition to medical therapy with corticosteroids and immunosuppressive agents, cryopexy to the retinal periphery and pars plana vitrectomy are playing an increasing role in the therapy of severely involved patients. Although the etiology of pars planitis remains obscure, clinical evidence suggests a strong association with multiple sclerosis. Furthermore, pars planitis has been linked with HLA-DR2, the same tissue antigen identified in patients with multiple sclerosis.