Ab initio calculations, including the GAUSSIAN−2 procedures, have been performed to determine the molecular structure and thermochemistry of the sulfur fluorides SFn (n=1–5) and sulfur fluoride cations SF+n (n=1–5) in the gas phase. Based upon a comparison between calculated and experimental heats of formation of SF6, standard enthalpies of formation are derived for the ten title species. Values for SF3, SF5, and SF+5 differ from literature values by more than 50 kJ/mol. Bond energies are also derived (uncertainties are 2σ): D°0(SF5–F)=444±6, D°0(SF4–F)=159±7, D°0(SF3–F)=398±7, D°0(SF2–F)=227±6, D°0(SF–F)=374±6, and D°0(S–F)=345±6 kJ/mol for the neutral species, and D°0(SF+4–F)=371±6, D°0(SF+3–F)=56±6, D°0(SF+2–F)=400±6, D°0(SF+–F)=372±6, and D°0(S+–F)=367±8 kJ/mol for the ions. Adiabatic ionization energies are calculated to be 10.13±0.20, 10.15±0.19, 8.36±0.18, 11.90±0.16, and 9.71±0.16 eV for SF through SF5, respectively. Calculated geometries, vibrational frequencies, entropies, integrated heat capacities, and vertical ionization energies are also reported. Energy levels for low-frequency vibrations are determined variationally.