We have observed various spectra of stimulated Raman scattering (STRS) in a-LiIO3 crystal in different scattering geometries under irradiation of an electro-optically Q-switched second harmonic YAG laser. It is shown experimentally that more multi-mode lattice vibrations .can be excited by extra-ordinary incident photons than by ordi-nary ones. We have also observed the first and second order Stokes and anti-Stokes scat-tering lines of E1 mode, which are strong in intensity. The first, second and third order polariton Stokes and anti-Stokes lines are observed, as well as a new spectral line with a frequency shift of 496 cm-1 in anti-Stokes frequency region, which may be attributed to interactions among polaritons with various modes.Fatigue phenomena of Raman activation for the crystal have also been indicated experimentally.