An homology model of human P-glycoprotein, based on the X-ray struc-ture of the recently resolved mouse P-glycoprotein, is presented. The model corresponds to the inward-facing conformation competent for drug binding. From the model, the residues involved in the protein-binding cav-ity are identified and compared with those in the outward-facing confor-mation of human P-glycoprotein developed previously based on the Sav1866 structure.