Foam treatment has moved toward held qualification as a practical method for gas shutoff in excessive gas/oil ratio (GOR) oil wells. In most field trials, the length of time that gas blockage is achieved is a few months, which may be too short for general acceptance. Laboratory and scattered held data show that addition of polymers can enhance foam performance in oil-reservoir rock. However, little is known about precisely how the addition of polymer improves the application-critical properties of a foam system. New experimental data for gas-blocking foams appear to show superior oil tolerance caused by the presence of polymer.