Intermolecular kinetic-energy operators are derived (in the rigid monomer approximation) for solute-solvent(n) clusters of the type B-A(n), where B is a molecule and A is either an atom or a molecule. The operators are obtained for a body-fixed frame embedded in the B moiety and parallel to the principal axes of that species. They are expressed in terms of intermolecular coordinates that represent the projection along the body-fixed axes of position vectors pointing from the center of mass of B to the centers of mass of the A species. The results are particularly useful for calculations on clusters in which A-B interactions dominate over A-A interactions in the intermolecular potential energy surface and/or there is minimal interaction between subsets of the A moieties. This utility is demonstrated in variational calculations of intermolecular states in the (1\1) isomer of anthracene-He-2. (C) 2003 American Institute of Physics.