The Raman shifts in naturally occurring cinnabar (HgS), realgar (As4S4) and orpiment (As2S3) have been measured at room temperature using a photoelectrically recording Raman spectrometer with He-Ne laser excitation at 6328 Å. By using the infra-red spectra of these compounds it was possible to make a partial assignment of these shifts. The number and symmetries of the Raman active phonons were calculated for the covalently bonded "sub-units". Most of the theoretically predicted vibrations were observed. The theory that realgar and orpiment are built from the same structural units could be supported.