The degradation of the model pollutant phenol with hydroxyl radicals generated from zero-valent iron and hydrogen peroxide has been investigated by means of HPLC analysis of the intermediates. The optimum conditions for degradation utilise the continuous presence of iron metal, acidic pH and relatively concentrated hydrogen peroxide (9.5 M). When less stringent conditions were used, the products obtained from the decomposition are broadly the same but are formed over a much longer timescale. The intermediates in the oxidation were identified as catechol, hydroquinone, benzoquinone, maleic acid and a relatively stable product, tentatively identified as an organic complex of iron and oxidised catechol. (c) 2005 Elsevier B.V. All rights reserved.