Interpenetrating polymer network (IPN) composed of silk sericin (SS) and poly(N-iso- propylacrylamide) (PNIPAAm) was prepared. The morphology of the IPNs, in which the SS phase was stained with ammonium cuprate, was examined with TEM and a relative homogeneous distribution of the two polymers was exhibited. The swelling behavior of the IPN hydrogels showed both temperature and pH dependences. The morphology of the IPNs, in which the SS phase was stained with ammonium cuprate, was examined with TEM and (d) a relative homogeneous distribution of the two polymers was exhibited. The swelling behavior of the IPN hydrogels showed both temperature and pH dependences.