An integrated system has been developed to remediate soils contaminated with pentachlorophenol (PCP) and polycyclic aromatic hydrocarbons (PAHs). This system involves the coupling of two treatment technologies, soil solvent washing and anaerobic biotreatment of the extract. Specifically, this study evaluated the effectiveness of the granular activated carbon (GAC) fluidized-bed reactor to treat a synthetic waste stream of PCP and four PAHs (naphthalene, acenaphthene, pyrene, and benzo(b)fluoranthene) under anaerobic conditions. This waste stream was intended to simulate the wash fluids from a soil washing process treating soils from a wood preserving site. The reactor achieved a removal efficiency of greater than 99.8% for PCP with conversion to its dechlorination intermediates ranging from 47% to 77%. Effluent, carbon extraction, and isotherm data also indicate that naphthalene and acenaphthene were removed from the liquid phase with efficiencies of 86% and 93%, respectively. Effluent levels of pyrene and benzo(b)fluoranthene were extremely low due to the adsorptive capacity of GAC for these compounds. Experimental evidence does not suggest that these compounds were chemically transformed within the reactor.