We have investigated the Zeeman effect of the R lines at 4.2°K in fields up to 88 kOe. The magnetic field has been applied both parallel and perpendicular to the C3 axis. When the external field is applied along the C3 axis, all of the lines split into two components. No splitting is observed in the perpendicular orientation. As the Kramer's degeneracy has already been lifted by the exchange field, the splitting is attributed to the removal of a sublattice degeneracy. It is well known that the spin system of Cr2O3 will flip when a critical field of about 59 kOe is applied along the C3 axis at 4.2°K. The spin-flop phenomenon has been seen in the optical spectra. From the splitting above the critical field there is tentative evidence of an anisotropic exchange interaction.