Ultrasonic compressional wave velocities have been measured in the laboratory for an Apollo 15 soil sample (15301, 38) under very low uniaxial stress and high vacuum conditions. The velocities measured range from 125 to 522 m/s. The velocities of the soil are stress dependent and are strongly affected by compaction history. Hertzian contact theory does not appear to fit the data adequately for the pressure range of the experiment. Moderate increases in temperature do not have a significant effect on the compressional wave velocities.