A transparent pressure vessel made of diamond has been used to study Raman spectra under pressure. It has the advantage that the relative displacement of the pressurizing pistons can be used to determine directly the change of density of the sample and to determine directly the Gru¨neisen parameter, and it can easily be heated or cooled over a wide temperature range by a gas stream. The relative displacement of the piston can also be used to identify the phase being examined, which is particularly valuable when a substance with a complicated phase diagram is being studied. The Raman spectra of the translational vibrations of ammonium fluoride II and of the rotational vibrations of anthracene have been studied using the cell.