The intermolecular potentials for the X2Σ and A2Π states of Li … Ne were studied by a variety of multiconfiguration, single configuration and perturbation methods (CASPT2). The A2Π excited state was calculated to have a well depth of 214 cm−1 at an internuclear spearation of 2.26 Å (ACPF) in excellent agreement with the 224 cm−1 derived from experimental data. A smaller well of 15.8 cm−1 was found for the X2Σ ground state at an intermolecular separation of 5.28 Å (ACPF). These results are in better agreement with experimental results than the previously reported pseudopotential calculations. The comparison of CI calculations with CASPT2 results shows that the latter is able to give good results for interacting systems. © 1993 John Wiley & Sons, Inc.