The results of calculations of SrTiO3 (100) Surface relaxation and rumpling xith two different terminations (SrO and TiO2) are presented and discussed. We have used the ab initio Hartree-Fock (HF) method with electron correlation corrections and the density functional theory (DFT) with different exchange-correlation functionals, including hybrid exchange techniques. All methods agree well on surface energies and on atomic displacements, as well as on the considerable increase of covalency effects , near the surface, More detailed experiments on surface rumpling and relaxation are necessary for further testing of theoretical predictions.