(CH3)(4)N+SO2CN- was prepared from (CH3)(4)N+CN- and SO2 and characterized by H-1, C-13, N-14 NMR, infrared, and Raman spectroscopy. The yellow salt is stable up to -10 degrees C, but solutions in SO2 decompose already at -50 degrees C in 1 day. The structure of the anion was predicted by ab initio calculations, suggesting C-s symmetry with a pyramidal coordination at the central sulfur atom with the following geometry: d(SO) = 146.7 pm, d(SC) 190.8 pm, angle(OSO) = 114.0 degrees, angle(OSC) = 100.8 degrees, and angle(SCN)= 173.6 degrees. The bent SCN arrangement is explained by negative hyperconjugation.