The infrared spectrum of S2F10 has been obtained for the vapor from 5 to 35 μ and for the solid at liquid nitrogen temperatures from 10 to 24 μ. The Raman spectrum, together with depolarization ratios, was obtained for the liquid. A vibrational assignment has been made consistent with either D4d or D4h, symmetry and all the fundamentals identified except two low FSSF bending frequencies and the inactive torsional frequency. A normal co-ordinate calculation located the bending frequencies at 37 and 57 cm.−1 while a simple potential energy calculation gave a torsional frequency of 89 cm.−1 corresponding to a potential barrier of 2780 cm.−1.