In this work, we measured the volatility of thermally stressed samples of RP-1 and RP-2 rocket propellant kerosenes by use of the advanced distillation curve method. This work is part of a large program at NIST and other laboratories geared toward improving the operability of the hydrocarbon component of liquid fuel packages. Measuring the properties of thermally stressed rocket propellant kerosene is a necessary component of this overall effort. This is motivated by the use of the kerosene as a coolant before combustion in the engine. Samples of RP-1 and RP-2 were stressed at 475 and 510 degrees C, at a pressure of 17 kPa (2500 psi), for residence times of 0.5 min. Volatility measurements revealed significant changes early in the distillation curves, becoming very pronounced at the higher temperature. The volatility measurements were supplemented with chemical analyses and a calculation of the enthalpy of combustion as a function of distillate volume fraction. We note that the increase in volatility is explained by the significant increase of very light (lower molecular mass) components produced during the thermal stress. We also note that the enthalpy of combustion follows the same pattern as the volatility, as we have noted in previous studies.