Curing kinetics of commercial polycarbosilane have been measured using differential scanning calorimetry in air between 140 and 220 degrees C. It was found that the total heat of curing increases linearly with temperature. At constant temperature, the rate of heat release can be described by the sum of a first-order kinetic term, and a transient term of much higher order, both depending on the fraction of remaining reaction enthalpy. Constants for both terms increase according to the Arrhenius law, with roughly the same activation energy of about 1.2 kJ mol(-1). The heat released in an additional non-isothermal experiment is well described by integration of the isothermal heat-release equations, suggesting that the rate of reaction can be described solely in terms of the fraction transformed and temperature.