Dibenzyl ether was decomposed in a batch bomb-type reactor both in supercritical water at 663-688 K and water density 387 kg m(-3) and in liquid water at 553-583 K and saturated vapour pressure. The reaction pathways were assumed to consist of pyrolysis, hydrolysis and decomposition of the major products, and their rates were determined. The pyrolysis rates are substantially consistent with published data for various atmospheres. The activation energies of the pyrolysis and hydrolysis pathways are 120 and 112 kJ mol(-1) respectively.