An implementation of a sum-over-states (SOS) formulation for the electronic g-tensor is reported and evaluated through test calculations. The calculations include contributions from the relativistic mass correction, the gauge correction and the second-order orbital Zeeman/spin-orbit coupling part. Five different configuration interaction (CI) based methods ranging from single excitation CI to accurate multireference methods were evaluated. The results were compared to experimental data and other high-level calculations. (C) 2003 Elsevier B.V. All rights reserved.