A new method for measuring the Poisson's ratio of polymer gels has been proposed and has been experimentally demonstrated. The method is based on different swelling behaviors of free and constrained gels. The Poisson's ratio of polyacrylamide gel, as a function of crosslinker concentration, has been measured using this method and has been found to be sensitive to the amount of polymerization initiator. The results are compared with results determined by other methods. © 1993 John Wiley & Sons, Inc.