The importance of antioxidants in inflammatory tissues has been studied in vivo. Degradation of homologous 3H-collagen powder by experimental granulation tissue induced by cellulose sponges in the rat was monitored as the radioactivity excreted in urine. By administering pharmacological doses of both vitamin E and selenium subcutaneously and by injection into sponges implanted subcutaneously, this breakdown of collagen was reduced. Injections in the sponges also arrested the maturation of the granulation tissue. Vitamin E and selenium are potential inhibitors of the free oxygen radicals from phagocytic inflammatory cells. It is therefore suggested that these radicals may play a rôle in the collagen destruction by granulation tissues, as in periodontitis.