We investigated the kinetics of biological removal of COD and nitrogen from a synthetic wastewater in a fluidized bed operating in batch mode. Synthetic wastewater consisted of diluted molasses, urea, KH2PO4, and MgSO4 resulting in COD/N/P = 100/10/2. The fluidized bed contained sponge particles surrounded by stainless-steel wires as support particles for microorganisms. The system was operated with different initial COD and nitrogen concentrations, and COD-nitrogen consumption profiles were obtained. From the initial slopes of these curves, the initial rates of COD and nitrogen consumption and kinetic constants were determined. The system operated under a COD limitation with no dissolved oxygen limitations. The kinetic analysis for COD removal has shown a Monod type of kinetics with possible inhibition on the K-s, term. Nitrogen removal rate data indicated an inhibition for nitrogen concentrations above 1,200 mg l(-1).