The gas-phase structure of dimethoxydisulfane (CH3O)(2)S-2 was determined by electron diffraction. The molecule is chainlike and of symmetry C-1. Selected experimental geometrical parameters are d(SS) 196.0(3) pm, d(SO) 165.3(3) pm, d(CO) 143.2(3) pm, alpha(OSS) 108.2(3)degrees, alpha(COS) 114.5(4)degrees, tau(SS) 91(4)degrees, tau(SO) +/- 7(3)degrees. Abinitio MO calculations at the HF/6-311G** level resulted in three conformational isomers originating from rotation about the two SO bond axes. The most stable conformer among these is in keeping with the gasphase structure. The two other rotamers are both of symmetry C-2. Infrared and Raman spectra of gaseous, liquid, and crystalline dimethoxydisulfane and its fully deuterated derivative were recorded. The 30 fundamental modes were assigned using the vibrational wavenumbers calculated for the three rotamers by the ab-initio MO method.