Temperature-sensitive hydrogels of poly(N-isopropylacrylamide) poly(N,N-diethylacrylamide), poly(N-n-propylacrylamide), copolymer of N-isopropylacrylamide and methylacrylamide, and copolymer of N,N-diethylacrylamide and N-tert-butylacrylamide were prepared. The swelling characteristics of the gels were studied and gel extraction of macromolecules, based on the solute exclusion by the gel network, were investigated.