The effects of a magnetic field on wastewater treatment with a fluidized bed biofilm reactor was investigated. With glucose being the sole carbon source, the activated sludge obtained from a real wastewater treatment plant was used as a seed. Magnetically loaded polystyrene beads at the size of 500-595 mum were used as support materials for biofilm formation in a fluidized bed biofilm reactor. Magnetic field application allowed the operation of the column at high liquid flow rates, thus external diffusion limitations on the biofilm surface were lowered and the efficiency of biodegradation was increased. Denser, thinner, and more active biofilm was obtained with magnetic field application, especially in pulsed form. As expected, the system performance changed with operational parameters, and the increase in substrate removal reached up to 26% with pulsed application of a 17.8 mT DC-magnetic field under optimum conditions.