Compressional and shear wave velocities were measured in water-filled Berea sandstone as a function of pore pressure, with a constant confining pressure of 300 bars. The measurements were made at room temperature, 145¿C, and 198¿C. At 145¿C, compressional velocity increased from vapor-saturated (low pore pressure) to liquid-saturated (high pore pressure) conditions, whereas shear wave velocity decreased. For compressional waves there was a velocity minimum and increased attenuation near the liquid-vapor transition. The results at 198¿C show decreases of both compressional and shear velocities and a small velocity minimum for compressional velocity without marked attenuation. At both temperatures, Vp/Vs and Poisson's ratios increased from steam- to water-saturated rock. The results are compatible with the mechanical effects of mixing steam and water in the pore space near the phase transition and may be applicable to in situ geothermal field evaluation.