Copolymers, poly(4-vinylpyridine-co-acrylic acid) (PVPA), with different composition were synthesized, and their palladium complexes were prepared. The catalytic properties of the palladium complex for the hydrogenation of aromatic nitro compounds were investigated. The palladium complex of PVPA can form a homogeneous system in ethanol. The optimum catalytic activity for hydrogenation of nitrobenzene was obtained when the molar content of 4-vinylpyridine (VPy) units in PVPA was 57.5% and VPy/Pd molar ratio was 6. The presence of 0.1 mol/l KOH can promote the catalytic activity to a great extent. In most cases, the hydrogenation of aromatic nitro compounds yields the corresponding aniline compounds almost quantitatively. The catalyst shows especially good activity for the hydrogenation of nitrophenols and nitroanisoles. The catalytic stability was also examined. (C) 2002 Published by Elsevier Science B.V.