Rate constants are reported for the 1-electron reduction of the azo dye Orange II in water (pH 7.0) by 10different α-hydroxy radicals. The radicals were created by pulse radiolysis of aqueous solutions of thecorresponding alcohol/sugar. The rate constants varied from 1 × 108 to 2.7 × 109 mol-1 dm3 s-1 and radicalswith β-hydroxy groups had the lowest rate constant. The reaction was found to be controlled by the reductionpotentials of the radicals, with steric influences having little effects. Good fits of the data were obtainedusing the Marcus equation with λ =140 kJ/mol.