First principles density functional theory calculations have been performed for the chemisorption of ethylene on the {111}, {100} and, {110} surfaces of Pd. On all the three low-index surfaces. the most stable site and geometry for C2H4 is that where the C-C bond axis is parallel to the surface along the bridge site. The calculated binding energies follow the trends: E-ads.111 < E-ads.100 < E-ads.110. The results show that the surface relaxation induces a significant shift in the level of the metal d-band. The calculated adsorption energies are only linearly correlated with the d-band centre of the surface atoms for the unrelaxed structure. (C) 2002 Published by Elsevier Science B.V.