Ab initio and DFT investigations on H2S-OH and (CH3)(2)S-OH adducts have shown that electron correlation is essential for an accurate description of the two-center three-electron S-O bonds in the adducts. Calculations at the BH&HLYP, B3LY-P, MP2, and CCSD(T) levels indicate that the S-O bond in the (CH3)(2)S-OH adduct is considerably stronger and shorter than that in the H2S-OH adduct. Our best estimate for the dissociation enthalpy at 298 K for the S-O bond in the (CH3)(2)S-OH adduct is 9.0 kcal/mol, which is in satisfactory agreement with experimentally derived values. (c) 2005 Elsevier B.V. All rights reserved.