The Sb/Si(110) 2 x 3 surface has been investigated by means of X-ray photoelectron diffraction (XPD). Low kinetic energies of the photoelectrons have been chosen to increase the surface sensitivity of the method. Simulation calculations have been carried out in order to test previously proposed structure models. The simulated diffraction patterns were compared with the experimental results by means of a R-factor analysis. The comparison indicates that at least part of the Sb atoms adsorbed on the surface form Sb trimers. (C) 2003 Elsevier Science B.V. All rights reserved.