The carbonyl products of the reactions of hydroxyl radicals with three vicinal diols (ethane-1,2-diol, propane-1,2-diol and butane-2,3-diol) have been identified and quantified. Hydroxyl radicals were produced by γ-radiolysis of N(2)O-saturated aqueous solutions. The reactions result in the formation of alkoxyl radicals (~15%) followed by β-fragmentation, and α-hydroxyl alkyl radicals that undergo H(2)O elimination. The latter process is part of a radical chain reaction at higher diol concentrations.