The temperature dependence of the rate constant for the reaction between OH radicals and H atoms has been determined in Ar-saturated solutions at pH 2. The reaction was studied in the temperature range 5-233degreesC. The rate constants at 20degreesC and 200degreesC are 9.3 x 10(9) and 3.3 x 10(10) dm(3)mol(-1)s(-1), respectively. The activation energy was found to be 8.2+/-0.4 kJmol(-1) (2.0+/-0.1 kcal mol(-1)). This value is lower than that expected for a diffusion controlled reaction. (C) 2002 Elsevier Science Ltd. All rights reserved.