Greater than 6-log reduction of viable Bacillus atrophaeus spores is achieved by treatment with supercritical carbon dioxide and hydrogen peroxide. Spores treated with CO2 + H2O2 released significantly more dipicolinic acid than untreated or pure CO2 treated spores. Substantial damage to the spore envelope was observed with transmission electron microscopy (TEM). These observations are consistent with damage to the outer layers of the spore and subsequent uptake of H2O2, resulting in death. (c) 2006 Elsevier BX All rights reserved.