1H and 13C NMR of dimethyl sulfoxide (DMSO)/H2O mixtures were measured, together with the IR of DMSO/D2O mixtures, to study the effect of the polar SO group on hydration of the CH groups. Chemical shifts were determined by the external double reference method, which provides the in situ volume magnetic susceptibility indispensable to the correction of the chemical shifts. The chemical shift of the water protons as the measure of the polarization of the water in the mixtures, δH2O, increases from 3.6 ppm at the water mole fraction XH2O = 0.05 to 4.8 ppm, the value for pure water, at XH2O = 0.80. It exceeds 4.8 ppm in the region of XH2O > 0.80 at 23.3 °C, indicating the presence of anomalously polarized water molecules, so-called hydrophobic hydration. The frequencies of the CH stretching vibration bands for (DMSO)/D2O mixtures, ν(CH), increase with increasing XD2O, implying the progressive depolarization and contraction of the CH bonds. ν(CH) values take maxima at XD2O = 0.96. The chemical shift of the CH ...