Ligand positions for Cr³⁺ at tetragonal sites in MgO are calculated from a lattice relaxation model. Using these ligand positions in conjunction with the parameters previously derived from the Cr³⁺:Al₂O₃ system, the author obtains the tetragonal crystal field parameters and the splittings of the low-lying energy levels for the present Cr³⁺ system. These results are compared with some experimental data and some fallacious calculations found in the literature are pointed out.