The physical aging of bisphenol A polycarbonate was studied using the differential scanning calorimetry technique. Cowie and Ferguson＇s model and Williams-Watts function were used to analyze the data. It is confirmed that the relation Delta H-infinity(T-a) = Delta C-p(T-g - T-a), where Delta H-infinity(T-a) is the value of the aging enthalpy for t = infinity, T-a the aging temperature, and Delta C-p the difference in the specific heat above and below the glass transition temperature (T-g), can be used to study quantitatively the physical aging of bisphenol A polycarbonate.