The Arrhenius parameters for the reaction of hydrogen atoms with methanol in aqueous solution have been determined by use of pulse radiolysis and electron paramagnetic resonance free induction decay attenuation measurements. At 25.5 degrees C, an absolute scavenging rate constant of (2.84 +/- 0.07) x 10(6) dm(3) mol(-1) s(-1) has been measured, and over the temperature range 10.2-86.4 degrees C, an activation energy of 29.4 +/- 0.8 kJ mol(-1) has been determined. These values have been used to make minor corrections to rate constant and activation energy values for the reaction of aqueous hydrogen atoms with iodomethane, iodoethane, and 1-iodopropane. For these three compounds at 24.3 degrees C, rate constants of (1.17 +/- 0.07) x 10(10), (1.39 +/- 0.05) x 10(10), and (1.42 +/- 0.06) x 10(10) dm(3) mol(-1) s(-1) and corresponding activation energies of 10.4 +/- 0.4, 11.8 +/- 0.4, and 11.9 +/- 0.4 kJ mol(-1) have been respectively calculated over the temperature range 9-52 degrees C. These fast reaction rate constants and the similarity of the activation energies suggest that the mechanism of reaction for all these iodoalkane scavengers is dominated by halogen abstraction, H-. + RI --> H+ + I- + (.)R. Comparison of the methanol scavenging rate to gas phase results suggests that tunneling which contributes to the gas phase reaction may be quenched in aqueous solution.