A: c~assical m~crosc?pi.c theory ~s ~resented for vibrational excitons interacting with the electromagnetic radiatIOn field III umaxIaI and biaXial molecular crystals. The coupled exciton-photon field leads to an eigenvalue equ~tion, the .solutions of which are polariton modes. It is shown how their frequencies w(k) can be calculated, If the oscillator strengths are known. It is further shown, that there is a close connection between factor-group splitting and La/TO splitting. That part of the effective field, whose range is bounded by the surface of the Lorentz sphere, produces factor-group splitting, while La/TO splitting is caused by the long-range part of the effective field, which is produced by the matter outside the Lorentz sphere.