Abstract. The work is devoted to the study of the regularities of laminar-turbulent transition in supersonic boundary layers. New experimental data are presented on the evolution downstream of natural disturbances in the boundary layer of a flat plate. The experiments were carried out in a low-noise supersonic wind tunnel T-325 of ITAM SB RAS at Mach number M=2.5. The measurements were made by a constant-temperature hot-wire anemometer in the scanning mode. The procedure of decomposition of the fluctuations of the boundary layer into temperature and mass flux disturbances is carried out.