The complementary techniques of infrared and Raman spectroscopy of simple molecular crystals in diamond anvil cells at pressures up to 12 GPa are briefly described. Recent results on the inorganic crystals of carbon disulfide, sulfur, the halogen cyanides, selenium dioxide and the boron trihalides, and the organic crystals of methanol, ethanol, benzene and the haloforms are reviewed. Evidence for solid state phase transitions, molecular distortions and perturbations of electronic states, as well as estimates of changes in intermolecular bond strengths, are discussed. Comparisons between the two types of spectra and between those observed at high pressures and low temperatures are also presented.