Many polycyclic aromatic hydrocarbons (PAHs) are known to be mutagenic or carcinogenic, and their contamination in soil and aquifer is of great environmental concern. Limited numbers of microorganisms including mycobacteria, Sphingomonas and white rot fungi were found to be capable of degrading PAHs with four or more fused aromatic rings. In white rot fungi, lignin peroxidases are believed to be involved in the degradation of PAHs. In addition to these enzymes, P450 monooxygenases in some fungi were implicated in the degradation of PAHs. The stimulation of PAH biodegradation by the addition of surfactants was observed with some of these microorganisms although the agents were inhibitory on biodegradation with some other microorganisms. Mathematical models were constructed to explain the effect of surfactants on biodegradation. Further studies should be carried out to select the best microorganisms and surfactants for applications to PAH bioremediation.