Solution miscibility of chitosan/polyethylene glycol fumarate blends dissolved in acetate buffer solution was investigated in different blend compositions by viscosity, density, and refractive index measurement techniques at 30, 40, and 50 degrees C. In order to quantify the miscibility of the polymer pair, degree of miscibility was studied by means of two criteria known as interaction parameters i.e., mu and a. On the basis of the sign convention involved in these criteria, these values revealed that the blend solution was miscible when the chitosan content was more than 80% (w/w) of the composition. The results were confirmed by density, and refractive index measurements. Furthermore, the results showed that the miscibility window of chitosan/polyethylene glycol fumarate blends was independent with respect to the changes in solution temperature. Therefore, these results suggested due to intermolecular hydrogen-bonding interaction between amino and hydroxy groups of chitosan and hydroxy groups of polyethylene glycol fumarate which play an important role in the formation of miscible phase. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013