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 ΔH∞(Ta) = ΔCp(Tg − Ta), where ΔH∞(Ta) is the value of the aging enthalpy for t = ∞, Ta the aging temperature, and ΔCp the difference in the specific heat above and below the glass transition temperature (Tg), can be used to study quantitatively the physical aging of bisphenol A polycarbonate. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1646–1648, 1999