Necrotizing scleritis may appear after trauma to the sclera. The authors studied 10 patients in whom necrotizing scleritis developed after ocular surgery. The interval between surgery and onset of scleritis varied from 2 weeks to 6 months. Nine patients (90%) were found to have an underlying autoimmune vasculitic systemic disease, which was subsequently treated with immunosuppression. One patient was found to have a local infectious process, which was treated with antibiotics. Appropriate studies led to the discovery and subsequent treatment of a systemic disease or an infectious process in 6 of the 10 patients; the other 4 patients had been previously diagnosed. Results of immunohistochemical studies on resected conjunctival and/or sclera suggest local immune complex deposition, increased HLA-DR expression, and increased helper T-cell participation in conjunctiva and/or scleral tissues after trauma in patients with underlying systemic autoimmune vasculitic disease. The results emphasize the need for meticulous diagnostic pursuit of potentially lethal systemic autoimmune vasculitic disease in patients with necrotizing scleritis after intraocular surgery.