Young's, shear and bulk moduli, Poisson's ratio and Lame parameters, longitudinal and transverse internal friction values and acoustic wave velocity anisotropy factors for three kinds of polycrystalline compounds, α-alumina, yttria-stabilized tetragonal zirconia polycrystal, (Y)TZP, and β′-sialon, (Si,Al)3(N, O)4, were simultaneously measured over a temperature range 295–1773 K, by an ultrasonic pulse sing-around method. These elastic moduli and Lame parameters decreases and Poisson's ratio increases with increasing temperature, suggesting activation of a shear mode in the high-temperature region. The high-temperature shear internal friction for (Y)TZP and sialon were more sensitive to relief of strain and softening of glassy phase at grain boundaries, respectively, compared with the dilational friction.