The rate constant for the reaction of hydrogen atoms (H*) with hydroxide ions (OH-) in aqueous solution has been measured from 100 to 300 degreesC by direct measurement of the hydrated electron ((e(-))(aq)) product growth rate. In combining these measurements with previous results, the reaction is observed to display Arrhenius behavior in two separate temperature regions, 3-100 and 100-330 degreesC, where the data above 100 degreesC show an obvious decrease in activation energy from 38.2 +/- 0.6 to 25.4 +/- 0.8 kJ mol(-1). The value of the rate constant is smaller than that estimated previously in the 200-300 degreesC range. The very unusual activation energy behavior of the forward and backward reactions is discussed in the context of transition state theory.