Polymorphonuclear neutrophils (PMN) participate in the inflammatory infiltrate of uveitis. At present, the importance of the role played by th e cells is largely unknown. We have studied the influence that an inhibitor of PMN recruitment could have on two types of uveitis: (1) endotoxin- induced uveitis (EIU), a disease mediated mainly by PMN and macrophages, and (2) experimental autoimmune uveoretinitis (EAU), a T-cell-mediated disease in which the early infiltrate is composed mainly of PMN. We have found that injection of NPC 15669 in rats significantly reduced the severit of EIU. More surprisingly, treatment of rats late in the process of EAU induction also inhibited the evolution of this disease.