The effect of Tween 80 and selected bacteria additions on the bioremediation of PAH contaminated landfill soil (70.38mgkg(-1)) was evaluated in a slurry phase bioreactor. A phenanthrene-degrading consortium was selected by enrichment cultures and used as autochthonous inoculum. The Tween 80 addition increased the aqueous concentration of both high and low molecular weight PAHs. In the experiment with Tween 80 and inoculum addition, added microorganisms improved (>90%) the biodegradation of two- and three-ring PAHs as well as of the four-ring PAHs pyrene and fluoranthene. Biodegradation of the higher molecular weight PAHs was about 30% in experiments with Tween 80 addition, with and without inoculum addition.