Abstract: The intensity of radiation backscattering in the near infrared range is calculated for the bilayer model of a strongly heterogeneous medium that can be treated as the system of “skull–brain” biological tissues. The Monte Carlo simulation procedure for multiple scattering in a bilayer randomly heterogeneous system is described based on the Bethe–Salpeter equation. As the single-scattering indicatrix, the Henyey–Greenstein phase function is used. The dependences of the backscattering intensity on the distance along the head surface between the radiation source and the detector are calculated. The form of these dependences turns out to be sensitive to the change of system parameters such as the scattering indicatrix anisotropy, the layer thickness, and the laser radiation wavelength. This feature can be used in medical diagnostics. An alternative approach is proposed to the calculation of the probability density distribution for the photon free path length. It is shown that beginning from the source–detector distance on the order of several transport lengths, the calculated intensity is in good agreement with the predictions of the diffusion theory.