A new piston-cylinder-type pressurizable dilatometer controlled by a stepper motor has been developed to measure the time-dependent bulk modulus and pressure-volume-temperature (PVT) behavior of polymeric materials. The dilatometer can be operated from 35 to 230 °C and at pressures of up to 250 MPa. The sample cell, which contains the sample and a fluorinated oil as the confining fluid, is totally submerged into a high precision oil bath to achieve a temperature stability of better than 0.01 °C. The instrument is calibrated with mercury and quartz. The total instrument volume is 4.0 cm3, of which 2.3 cm3 is the sample cell; the total volume can be measured with an average absolute error of better than 5.0× 10-4 cm 3. To demonstrate the instrument's capabilities, the time-dependent bulk modulus and the PVT behavior of a polystyrene are obtained and compared to the literature.