Problems of the mixing of turbulent jets with a surrounding gas such that the velocities and temperatures of the jet and surrounding gas differ by a substantial factor (several times), and problems of turbulent mixing in the presence of chemical reactions, are of great practical interest at the present time. In view of this, and the use of the classical solution of the problem of mixing of an incompressible fluid (see e.g. [1], [2]), more and more theoretical and experimental work is being devoted to the study of the turbulent mixing of a compressible fluid, and to mixing in the presence of chemical reactions (see e.g. [3]–[8]). The analysis of turbulent mixing requires the solution of a complete system of equations of discontinuity, motion, energy and diffusion, which is too complicated at the present time, in particular because the transport and chemical properties of turbulent flow are almost entirely unknown and the existing empirical constants are extremely inaccurate. The assumption is therefore usually introduced that the gradient of the pressure in the direction normal to the streamline is small compared with the other flow parameters and can be neglected. The boundary layer equations can then be used for describing the mixing process. The present article considers, within the approximation of the boundary layer theory, the mixing of two homogeneous flows of compressible fluid with Prandtl numbers different from 1; cases where there is a great difference between the temperatures and velocities of the mixing flows are considered. When investigating plane laminar and turbulent jets of incompressible fluid, L.G. Loitsyanskii [9] introduced variables similar to those proposed by Mises for the study of a laminar boundary layer, which enabled laminar and turbulent equations to be reduced to the same form. By a similar procedure in the case of the mixing of a compressible fluid, i.e. introducing new independent variables, the equations of turbulent mixing can be reduced to the form of the equations of laminar mixing, and hence solutions can be applied to them using the same algorithm as was developed for the solution of the equations of laminar mixing (see [lO]). The introduction of new variables enables us to distinguish the solution of the boundary value problem for the flow in the mixing zone, which offers considerable mathematical difficulties, from the problem of computing the temperature and velocity profiles for concrete sections, where no mathematical difficulties are involved but use is made of empirical magnitudes.