[en] To test the theory of the multiple scattering of fast charged particles experimentally studied was the magnitude of the square transverse shift of 15 MeV protons in plexiglas with the thickness from 4 to 13 cm. The experiment was conducted on the medico-biolocal proton beam of the ITEP synchrophasotron. The beam axial symmetry was determined by a solid nuclear detertor, and the angular scattering - by measuring the radial distributions of the proton current density at different distance from the collimator in air without the scatterer with the help of an ionization chamber. The investigation has shown that the theoretical value of the proton mean square transverse shift in plaxiglas is in a good agreement with the experimental data. Comparative evaluations of the experimental data and other available results were made