Supermolecular model of the intermolecular interaction energy is studied. The correlation energy components are calculated by using the many-body perturbation theory (MBPT) in the canonical representation as well as in the localized one. The components of the corrections of the different order are analyzed individually. The effects of the localization procedure and the basis set are also investigated. An H2O trimer is used to study the two- and three-body components of the interaction energy. © 1993 John Wiley & Sons, Inc.