Molecular structure of the ligand binding domain of hAhR has been modelled by homology modelling techniques and used for docking simulations with dioxin and nine more xenobiotics and endogenous ligands. The study evidences that different sites may bind these ligands, whereas only one binding site has been previously indicated by past studies on the mouse homologous receptor. The differences in the sequence of mouse and human AhR ligand binding domain may explain this observation, being most of them in the additional sites observed. Preferences of the evaluated ligands for the different sites are reported and discussed in view of their functional role. (C) 2011 Elsevier Inc. All rights reserved.