In laboratory experiments, borehole stress concentrations caused by far-field uniaxial stress produce measurable variations in compressional wave velocities near the borehole. Uniaxial stress was applied perpendicular to the axis of a borehole drilled through a sandstone block. Inside the fluid-filled borehole, refracted compressional waves were propagated in the rock parallel to the borehole axis at discrete azimuths, producing a scan of velocity versus azimuth. As uniaxial stress increased, significant variations of compressional wave velocity with azimuth developed, of the order of 10% variation. The azimuth of velocity minima provides an excellent indicator of the direction of maximum far-field uniaxial stress, accurate to 5¿. The detailed variation of velocity with azimuth, while approximately sinusoidal, has sufficient character to provide new information about the rock. One interpretation yields the curvature of the velocity versus stress curve of the rock. ¿ American Geophysical Union 1996