A density measurement system was developed using a vibrating tube densimeter prototype for high temperature and high pressure (DMA-HDT). Fully automatic density measurements over a large temperature and pressure range were realized with the help of the specially developed controlling software. Currently, the unit is applicable for temperatures from 298 K to 523 K and pressures from atmospheric pressure up to 100 bar. The estimated total error in the density measurements is +/-0.0002 g/cm(3).