The magnetic susceptibility of the Pr4+ ion in dilute solid solution in CeO2 has been measured as a function of temperature between 85 and 300°K. The results are compared with the theory for the 2F term of the f1 configuration split by spin–orbit coupling and by the ligand field arising from the stereochemistry of a regular cube. They can be accounted for by the model, although the ‘best fit’ set of parameters for the ligand field does not give a value for the sixth order spherical harmonic terms which is in good agreement with expectations from related systems where the co-ordination is from an octahedron of oxygen ligand atoms.