Polarization effects in crystal acoustics include birefrin- gence, elliptical polarization under deflection of a wave vector from an acoustical axis, natural acoustical activity, and so on. Some polariza- tion effects are possible in nonlinear crystal acoustics. The character- istics of polarization effects in crystal acoustics are discussed The ex- perimental observation of the elliptical polarization of shear elastic waves under the direct electric field is fulfilled. The measurements have been carried out in X3 direction in piezoelectric crystals LiNbO3 and LiTa03 at frequencies of 500-900 MHz. The theory of the effect on nonlinearity of piezoeffect is discussed. A theoretical analysis pre- dicts that if an elastic wave propagates along a threefold acoustical axis of crystal, the second-harmonic polarization will depend on funda- mental wave polarization. If along the X1 axis, the second harmonic polarization would be along the X2 axis; but if the fundamental wave is polarized along the X2 axis, the second harmonic would have the same polarization. Such phenomena are observed in a cubic crystal, as well. Experiments were performed on the following crystals: Si02, LiNbO3, A1203, and Si.