Abstract Quantum-chemical ab initio calculations have been performed for the van der Waals interaction between helium and oxygen atoms in their respective ground states: He( 1 S)+ O( 3 P). As long as fine-structure effects are neglected, there are two low-lying electronic states, 3 Σ − and 3 Π resulting from the degeneracy of the O( 3 P) ground state. Both states are purely repulsive at the SCF level, after inclusion of electronic correlation by the CEPA method they exhibit shallow van der Waals (dispersion) minima at large interatomic separation: R ϵ = 3.61 A, ϵ = 1.0 meV ( 3 Σ − ) and R ϵ = 3.05 A, ϵ = 2.3 meV ( 3 Π). The analysis of the results shows the very slow convergence of the dispersion interaction with increasing basis size, while SCF repulsion and the repulsion due to the change of the intra-atomic correlation are obtained reasonably accurately with moderate basis stes. Van der Waals coefficients C 6 , C 8 , C 10 , potential curves of the type HFD (i.e. Hartree-Fock plus damped dispersion) and the influence of fine-structure effects (mainly spin-orbit coupling) on the shape of the adiabatic potential curves are discussed as well.