The shielding tensor surfaces for the Xe-Xe, Xe-Kr, Xe-Ar, and Xe-Ne dimers are calculated as a function of separation, using gauge-including atomic orbitals (GIAO) at the Hartree-Fock level, and also using density functional theory with the B3LYP hybrid functional. Since the highest quality potential energy functions are available for these systems, the available experimental data (temperature dependent second virial coefficients of the nuclear magnetic resonance chemical shifts) are from measurements on well-defined physical systems (Xe at low mole fraction in the gas phase), and the relation between the observed quantity and the shielding function is well-defined, these systems provide a means by which the dispersion component of the isotropic shielding function of Xe-Rg can be determined. The parallel component of the intermolecular shielding tensor is small and nearly independent of the method of calculation. Therefore, the dispersion component of the perpendicular component of the shielding function can be determined. (C) 2003 American Institute of Physics.