Natural PAHs biodegradation was shown in the soil of former gasworks site and the influence on biodegradation efficiency of sawdust addition studied. Cultures enriched by serial transfer through a mineral medium contraining either fluorene, phenanthrene, anthracene, fluoranthene, or pyrene were used to obtain several bacterial communities. The obtained consortia were able to grow on different individual PAHs as their sole carbon source and consisted of a mixing of gram-negative and gram-positive bacterial strains. The reintroduction of the bacterial communities into sterilized polluted soil microcosms was investigated by following the PAHs and the microbial levels in the soil.