When relativistic effects are taken into account, the second-order spherical component of the crystal field can cause a splitting in the 8S7/2 ground state of Eu2+ in low-order perturbation theory. This splitting is closely related to the free-ion quadrupole splitting. The contribution from this mechanism to the crystal-field parameter b20 for Eu2+ in CaWO4 is estimated from electron paramagnetic resonance and electron–nuclear double resonance measurements on the divalent europium ion. It is found that the remaining contributions to b20 do not have a simple dependence on lattice parameters or low-lying energy levels and may be influenced by dynamic processes.