The toxicity of free radicals produced in cellular oxidative reactions is well known. In eye tissues, the frequent exposure to light poses an additional source of free radical. Peroxidase is the major enzyme system i the retinal pigment epithelium to prevent accumulation of H2O2. The detail d biochemical nature of this enzyme in the retinal pigment epithelium and its identity of the peroxidase of other tissues is not known. The present specific aim is to purify the major peroxidase from the retinal pigment epithelium, compare its properties with that of erythrocytes, granulocytes, and to produce a specific antibody for the purified peroxidase. The antibo y will be used to visualize its location in the eye tissues.