The behavior of optical‐medium parameters governing the efficiency of stimulated Brillouin scattering (SBS) with an increase in the pump‐radiation wavelength is studied, and the range of media promising for accomplishing the phase self‐conjugation in the course of SBS in the midinfrared region of the spectrum is determined. The SBS effect in the 10‐μm region is realized experimentally in a fiber waveguide made of KRS‐5. The result obtained is in good agreement with the calculated SBS gain (0.14 cm/MW) and decay time of sound (∽200 ns) in KRS‐5. It is noted that the attainment of fairly high efficiencies of SBS reflection and phase self‐conjugation for the above‐threshold intensities of excitation are controlled only by the level of technology for fabrication of fiber waveguides from infrared materials, the properties of which can still be much improved.