Sericin has been considered to serve as a lubricant to facilitate the formation of cocoon fibers, being present between the silk gland cells and the fibroin.’) However, other biological roles of sericin are unknown. Our study provided the evidence for the antioxidant action of seri cm. We speculate that sericin may become an antiox idant defense barrier against the oxidative stress from the external environment to protect the cocoon and Silkworm.