The white rot fungus Phanerochaete chrysosporium was utilized for the degradation of a model chlorinated organic compound, i.e., 2-chlorophenol, using three different reactor configurations: a batch fermenter, a chemostatic reactor with the fungus immobilized on a silica-based porous biocatalyst support, and a packed-bed reactor where the fungus was immobilized on balsa wood particles. A comparison of the effectiveness of these reactor configurations was made by determining the overall first-order kinetic rate constant for the degradation process for each one of the reactors. The packed-bed reactor proved to be the most effective configuration examined in this study because of the low shear and the presence of a solid support. Therefore, this type of reactor was studied in greater detail. In the packed-bed reactor oxygen was supplied by either sparged air or hydrogen peroxide additions. The degradation process was followed by taking samples from five different-ports mounted alongside the packed-bed column. Glucose, nitrogen, 2-chlorophenol, chloride ion, and ligninolytic enzyme concentrations were measured in each sample. In this reactor the fungus was able to mineralize 2-chlorophenol in concentrations up to 500 ppm. About 80% to 94% of the chlorine initially present in the 2-chlorophenol fed to the system was recovered as chloride ion.