Biodegradation of a mixture of PAHs was assessed in forest soil microcosms performed either without or with bioaugmentation using individual fungi and bacterial and a fungal consortia. Respiratory activity. metabolic intermediates and extent of PAH degradation were determined. In all microcosms the low molecular weight PAH's naphthalene, phenanthrene and anthracene, showed a rapid initial rate of removal. However, bioaugmentation did not significantly affect the biodegradation efficiency for these compounds. Significantly slower degradation rates were demonstrated for the high molecular weight PAH's pyrene, benz[a]anthracene and benz[a]pyrene. Bioaugmentation did not improve the rate or extent of PAH degradation, except in the case of Aspergillus sp. Respiratory activity was determined by CO(2) evolution and correlated roughly with the rate and timing of PAH removal. This indicated that the PAHs were being used as an energy Source. The native microbiota responded rapidly to the addition of the PAHs and demonstrated the ability to degrade all of the PAHs added to the soil, indicating their ability to remediate PAH-contaminated soils. (C) 2009 Elsevier Ltd. All rights reserved.