Bioremediation of organic wastes is often a cost-effective technology for the in situ treatment of contaminated soils. In this study, the possibility of increasing the rate and extent of biodegradation for phenathrene, anthracene, fluoranthene, and pyrene in an industrial PAH contaminated soil via vitamin mixture supplementation was explored. Soil contained with PAHs was obtainecl from the Bayway refinery site formerly owned by Exxon (Linden, NJ). Experiments were conducted in which the contaminated soil was amended with a mixtures of four vitamins (niacin, biotin, folic acid, and panthothenic acid). Peat moss, a common soil amendment, was also added in some experiments. The results showed that different vitamin mixture concentrations had a significant effect on the biodegradation rate and extents of phenanthrene, anthracene, fluoranthene, and pyrene, provided that peat moss was absent. The presence of peat moss resulted in an increase in the rate and extent of PAH biodegradation, independently of the presence of vitamins.