Reconstruction of electromagnetic parameters of artificial materials is an urgent problem [1], [2]. In practice, as a rule, these parameters cannot be directly measured. Therefore, methods of mathematical modeling must be applied. Conventional waveguide measurement equipment employs network analyzers and dielectric samples having the simplest shape of a parallelepiped adjusted to the walls of a standard rectangular waveguide. Such setups open the way to use well-developed analytical-numerical techniques [3], [4] of determining permittivity and other parameters of the inclusion using accurate closed-form solutions and asymptotic approximations. This work is a continuation of the series of papers [3], [4] devoted to the analysis of inverse problems of finding permittivity and permeability of layered materials. We apply a specially developed mathematical and numerical technique that combines analytical and numerical approaches providing the results with guaranteed accuracy. Particularly, we develop the methods [3] of determining permittivity and permeability tensors of anisotropic materials in a rectangular waveguide.