Measurements of the specific dissipation factor, Q-1, have been made in saturated rock as a function of effective pressure. The measurements were made of two different frequencies, one in the range of 100 to 250 Hz and the other in the range of 7 to 9 kHz, using the resonant bar method. In saturated rock, Q-1 is lower at the lower frequency, and the difference between the values of Q-1 measured at the high and low frequencies decreases as effective pressure increases. At effective pressures greater than 200 bars, the Q-1 of saturated Berea sandstone measured at 200 Hz approaches that of dry Berea sandstone measured at 7 kHz.