N-isopropylacrylamide (NIPAAm) was used to synthesize NIPAAm homopolymer (nonionized) andNIPAAm-sodium methacrylate copolymer (ionized). The swelling equilibria for both gels were obtained in aqueoussolution of ethanol with concentration ranging from 0 to 100%(by mass) at 25℃. The swollen gel in water shrankfirst with the addition of a small amount of ethanol and then reswelled with further addition of ethanol showing notonly a discontinuous volume phase transition but also a typical reentrant phenomenon. A thermodynamic modelbased on the UNIQUAC with the "free-volume" contribution was applied to correlate and predict the swellingbehavior of the poly(NIPAAM)-gels in ethanol-water mixture.