The ability of an immobilized bacterial co-culture to degrade selected dichlorobiphenyls was investigated with the aim of developing a process for the degradation of polychlorobiphenyls in wastewater Aerobic fixed-bed bioreactors were developed by immobilizing cells of the co-culture on silica beads, frosted glass bends and polyurethane foam cubes. Significant degradation and dechlorination was achieved in batch conditions. The kinetics of production of the main metabolites of the degradation, including meta-ring-fission products, chlorobenzoic acids and chloride ions, were studied for each dichlorobiphenyl in each bioreactor. The distribution of bacterial cells in the biofilms developed was observed by scanning electron micrograph. Some kinetic parameters of the polychlorinated biphenyl-degrading member and other bacteria in the co-culture were determined.