A chitosan-supported palladium catalyst was prepared by immobilization of palladium on glutaraldehyde crosslinked chitosan followed by in situ chemical reduction. This catalyst was successfully used for the degradation of 4-nitroaniline 4-NA) in the presence of sodium formate, used as the hydrogen donor. The reaction product was 1,4-phenylenediamine. The degradation was favored by acidic pH. A 10 to 15 excess of formate (compared to 4-NA) is required to achieve complete degradation of the substrate. The reaction appears to be limited to the external layers of the catalyst: small particle size is required to optimize the degradation kinetics. Alternatively, an increase of catalyst dosage is required to increase kinetic rates but at the expense of palladium consumption. (C) 2004 Wiley Periodicals, Inc.