The radiation chemical yield of hydrogen peroxide has been determined in the gamma-radiolysis of water at neutral pH. Methanol, ethanol, and bromide have been used as OH radical scavenaers in order to explore the temporal dependence of hydrogen peroxide formation at elevated temperatures. The scavenger results at all temperatures confirm that OH radicals are the sole source of hydrogen peroxide at short times in the gamma-radiolysis of water. Variation in dose rate by a factor of 20 shows no influence on the yield. With increasing temperature the yield of hydrogen peroxide is found to decrease, and the microsecond radiation chemical yields at low scavenger concentrations are found to be G (H2O2) = 0.78-2.43 x 10(-3) T (degreesC) molecules/100 eV for methanol as a scavenger, and G (H2O2) = 0.74-2.40 x 10(-3) T (degreesC) molecules/100 eV for bromide. The scavenger concentration dependence of the yields at elevated temperatures is discussed. Assuming an activation energy of 71 kJ mol(-1) the thermal decomposition reaction rate constant for hydrogen peroxide in aqueous solution is estimated to be 6.5 (+/-0.2) x 10(5) exp(-71 kJ mol(-1)/RT) s(-1).