Dimethyl thiourea is a highly specific hydroxyl radical scavenger. The antiinflammatory potential of this hydroxyl radical scavenger was studied in Lewis rats sensitized with soluble lens protein. Intraperitoneal injection of dimethyl thiourea into the experimental animals at the onset of the disease resulted in marked reduction of intraocular inflammation, hemorrhage and edema, and eliminated the retinal and choroidal necrotizing vasculitis that was characteristic in untreated animals. These findings indicate that dimethyl thiourea may act as a potent antiphlogistic agent in the treatment of experimental lens-induced uveitis.