Boundary conditions in the statistical theory of dynamical diffraction are shown to be closely related to the interference effect between the incident wave and the forward-diffracted wave. The propagation of the incoherent diffracted beams is analysed in the case of Laue geometry. For E=0 (E, static Debye-Waller factor), the authors then obtain generalized energy transfer equations which are valid in the whole influence region of a point radiation source. The most significant physical difference from previous formulations concerns the behaviour of integrated intensities for crystals such that chi ² tau T>>1 ( chi is the reciprocal of extinction distance, tau the correlation length of the lattice distortion and T the crystal thickness along the incident direction).