Insulin was bound physically to diazopolystyrene quenched with β—naphthol. When β—naphthyl—azo—polystyrene—insulin thus prepared was administered to the jejunum of rabbits, there was a significant increase in plasma insulin concentrations, followed by a significant fall in blood glucose. The plasma insulin concentrations following administration of β—naphthyl—azo—polystyrene— insulin were 2–3 times higher than those following infusion of crystalline insulin. These results indicate a possible means of protecting insulin molecule from digestive destruction. (Endocrinology91: 320, 1972)