Using methods of acoustic microscopy, we study a microstructure of materials produced by the process of vulcanization of mixtures of polyvinylchlorides and butadiene-nitrile caoutchoucs. The mixtures under study differ by the compatibility of components and degree of homogenization. When an acoustic microscope is used, the contrast of elements of microstructure is determined by variations of local mechanical properties but not dielectric properties as it is in the cases of light and electronic microscopy. Because of this feature of acoustic microscopy, acoustic patterns may represent in detail the peculiar properties of distribution of the components that differ by density and elastic characteristics. As a result, we have an opportunity to estimate the basic parameters of phase morphology of heterogeneous polymeric mixtures.