The pressure-volume-temperature (PVT) properties of three commercial samples of poly( dimethylsiloxane) are studied experimentally and theoretically in the temperature range 25-150 degrees C and for pressure to similar to 3 kbar. The Tait equation is employed to represent the data at elevated pressure. Isothermal compressibilities are computed for the three samples. The melt data are analyzed in terms of the Simha-Somcynsky hole theory, and scaling parameters of pressure, volume, and temperature are obtained. Satisfactory agreement between theory and experiment is found over the entire range of experimental pressures.