A three year field study was conducted to investigate the adaptive significance of color polymorphism in the cricket frog, Acris crepitans, in Illinois, U. S. A. Effective population breeding sizes were determined at seven different locations. Population characteristics in Illinois were compared with those from Texas. The three color morphs appear to be of equal survival value for cricket frogs in Illinois. Although strong selection may occur in Texas, small effective breeding sizes suggest that chance plays a major role in determining color morph frequencies in Illinois.