We report the preparation and characterization of a Pt/gamma-Fe2O3 nanocomposite catalyst and its novel catalytic properties for the selective hydro.-enation of ortho-chloronitrobenzene (o-CNB). The catalytic hydrodechlorination of the hydrogenation product ortho-chloroaniline (o-CAN) over the catalyst was fully suppressed for the first time at complete conversion of o-CNB. The nanocomposite catalyst also exhibited excellent catalytic activity and stability for the reaction of interest, suggesting that it may be suitable for industrial application. The magnetic property of the Pt/gamma-Fe2O3 nanocomposite provided a convenient route for separating the catalyst from the reaction system in an applied magnetic field. (C) 2004 Elsevier Inc. All rights reserved.