A three-level full factorial design has been conducted to assess the influence of gas flow-rate, ozone concentration and reaction time on the remediation of soil contaminated with four PAHs (namely acenaphthene, phenanthrene, anthracene and fluoranthene). Under the operating conditions investigated, reaction time and ozone concentration seem to exert a slight positive effect, whereas gas flow-rate does not affect the process efficiency. Average conversions (related to non-ozonated samples) are in the proximity of 50, 70,60 and 100% for acenaphthene, phenanthrene, anthracene and fluoranthene, respectively. A high conversion percentage is obtained in the first minutes of the process. Ozone decomposition on soil surface can be modelled by its reactions with easily oxidizable organic matter, recalcitrant ozonation intermediates and inorganic active sites. (C) 2009 Elsevier B.V. All rights reserved.