Equations of mechanics of multicomponent two-phase compressible disperse mixture, in which heat and mass transfer processes and chemical reactions take place, are derived. Interphase energy transfer in particular during component transition from one phase to another is analyzed. Problems of allowance for phase imperfections and of conditions of thermodynamic equilibrium are considered. Explicit expression is derived for the dissipation function, linear phenomenological relationships are analyzed, and singularities of the structure of direct and cross effects which develop in the system are disclosed. The state of investigations related to mechanics of heterogeneous mixtures is presented in the survey [1], We would point out here that Rakhmatulin was the first to formulate a closed system of equations for determining mixtures of compressible phases [2], The system included equations of mass and momenta of phases and equations for the over-all pressure. The proposed in it scheme for defining the force of interaction between phases is peculiar to a polyphase mixture and not to the multicomponent one. These concepts were applied to a saturated porous medium consisting of a mixture of two compressible phases without phase transitions. A scheme for defining energy exchange between phases and thermodynamic equations were proposed. A system of hydromechanical equations for a two-phase single-component disperse mixture of compressible phases was considered in [4], Phase transformations, which complicate the interphase exchange of energy and momentum, were assumed to be present in the mixture. This model was later supplemented. by an allowance for surface effects and small scale flows around inclusions [5], The equations of balance of mass, momentum and energy of components in a multi-speed form were formulated in [6–10], No clear distinction between homogeneous and heterogeneous mixtures was made in a number of investigations of this kind [1], with the analysis reduced to that of equations of conservation of components. It should be noted that in the case of a homogeneous mixture it is not necessary to have separate equations of momentum and energy for each component. Such separation (hence, also, the setting of momentum and energy exchange) must be made by phases only i.e. in the case of a heterogeneous mixture in which in addition to other conditions it is necessary to take into account parts of volume and interphase surface of mixture occupied by each phase [1] (this problem does not arise in the case of homogeneous mixtures). An important aspect of the definition of a heterogeneous mixture is the correct determination of the structure of terms which define the interaction between phases which takes place at interphase surfaces.