The bioavailability of polycyclic aromatic hydrocarbons (PAHs) in coal-tar contaminated soils plays an important role in determining the risk of these compounds to the environment and humans. Developing an understanding of organic compounds bioavailability will assist in improving risk assessment and developing bioremediation strategies. In the first part of study, the degradation of 16 EPA priority PAHs in soil slurry reactors were investigated along with the change in microbial population. Using DAPI-stained organisms, maximum microbial populations were found to correspond with the depletion of 2- and 3-ring PAHs. Degradation of PAHs was sequential with the 2- and 3-ring PAHs degrading first, followed by the 4- and 5-ring PAHs. There was negligible degradation of 6-ring PAHs. The Modified Gompertz equation, an empirical model, was used to estimate the lag phase, degradation rate, and maximum degraded fraction of individual PAHs. The Monod equation was also applied but did not model the experimental data well especially the change in microorganism population. In the second part of study, several chemical methods were performed to assess the bioavailability of PAHs in three coal-tar contaminated soils from former manufactured gas plant (FMGP) sites. The methods tested were hydroxypropyl-β-cyclodextrin (HPCD), persulfate oxidation, acetone-water mixture extraction, butanol extraction, and solid phase extraction using XAD-2. Residual PAHs in each soil following extraction were compared with the PAHs remaining after biodegradation in soil slurry reactors. Of the five methods tested, the XAD-2 desorption method was determined to the best method for predicting the bioavailability in coal-tar contaminated soils.