Abstract The oligomerization of hydroquinone (HQ) under oxidation with oxygen has been investigated in aqueous alkali. The high reactivity of HQ compared with phenol has been noted. A mechanism of radical recombination accompanied by proton migration is proposed for this reaction. The constancy of the rate of auto-oxidation up to 100% conversion of HQ is related to rapid recombination of semiquinone radicals and their transition into phenol form. There is consequently no reduction in the concentration of OH groups during this period. The reactivity of oligohydroquinone during auto-oxidation decreases significantly, as the length of the macromolecules increases, because of their transformation into stable macrosemiquinone radicals.