Measurements were made of the hypersound velocity in some viscous liquids - in the wide interval of temperature by stimulated Mandelshtam-Brillouin scattering spectra. Unusual temperature dependence of hypersound velocity was observed in glycerol. It was shown that all experimental results with usual temperature dependence of velocity in viscous liquids can be described by Isakovich-Chaban theory formulas, but the physical grounds of the theory require new investigations.