The accuracy of the atomic mean-field approximation (AMFI) to the spin-orbit interaction Hamiltonian is evaluated for the paramagnetic contribution to electronic g-tensors. A variety of different substances are tested for this purpose for restricted open-shell Hartree-Fock and multi-configuration self-consistent field wave functions. In most cases the introduced error is significantly lower than errors of wave function parameterization. Considering the substantial computational savings, it is argued that the mean-field approximation is warranted given the resolution available in current electron spin resonance experiments. (C) 2002 Elsevier Science B.V. All rights reserved.