The Raman and infrared spectra of 1,4-dithiane-1-oxide are reported in the frequency region from 4000 to 130 cm−1, for polycrystall ine samples. The observed bands are assigned on the assumption of a Cs chair form with axial conformation. The fundamental frequencies are discussed and compared with those of 1,4-dithiane, pentanethylene sulfoxide and 1,4-oxathiane-4-oxide, The vibrational coupling among skeletal and S=0 deformations is discussed.