Abstract The electrochemical oxidation of 6,8-dioxypurine has been studied in aqueous solution at graphite electrodes. At pH 2.0 the single voltammetric oxidation peak observed corresponds at a 2 e − −2 H + oxidation of 6,8-dioxypurine to a very unstable quinonoid which is attacked by water to give a 4,5-diol intermediate. The latter diol can be observed using thin-layer spectroelectrochemistry and has been isolated using HPLC techniques. The diol is hydrolyzed in solution to 5-( N-formyl)carboxamide-5-hydroxyhydantoin which in turn decomposes to 5-hydroxyhydantoin-5-carboxylic acid and 5-hydroxyhydantoin-5-carboxamide. Hypoxanthine is electrochemically oxidized at more positive potentials to 6,8-dioxypurine which is immediately further oxidized to the latter products. At pH 7.0 the oxidation of 6,8-dioxypurine follows a similar pathway to that at pH 2.0. In the case of hypoxanthine at pH 7.0 the major oxidation reaction appears to proceed by initial formation of 6,8-dioxypurine but alternative minor routes are also apparently available.