The changes in pore volume of jacketed dry sandstone samples have been measured under hydrostatic pressures over the range 50 to 1,000 bars (14,504 psi). The percent change in pore volume at each pressure and the pressure coefficient of change of pore volume have been computed. All measurements were made at room temperature. The total change in pore volume when the hydrostatic pressure was increased from 50 to 1,000 bars was found to be about 7.5 percent of the pore volume for a sample of Steven sandstone (porosity 18.5 percent) and approximately 3.0 percent of the pore volume for a sample of Berea sandstone (porosity 19.4 percent). The coefficient of change of pore volume with pressure is found to decrease rather rapidly with increasing pressure up to around 500 bars. Thus pressure changes applied to rock become much more important when the original geostatic load on the rock is small.