The structure, thermochemistry, and reactivity of numerous sulfur oxyfluorides have been examined in a combined theoretical and experimental study. Calculations were carried out for SOFn=0-5, SO2Fn=0-3, SO3Fn=0-1, and their corresponding anions using the Gaussian-2 procedure. Structural parameters, standard entropies, and integrated heat capacities were calculated at the MP2(full)/6-31G(d) level of theory. Electron affinities, vertical detachment energies, fluoride affinities, neutral bond dissociation energies, and neutral and anion heats of formation were derived from the G2 total energies (0 K) and enthalpies (298 K). This comprehensive dataset of thermochemical properties for both neutrals and anions is compared to available experimental results and to previous theoretical treatments of individual S/O/F compounds. A number of significant discrepancies are noted. Using a selected ion flow tube, a series of laboratory measurements were made to test the theoretical results and to examine SOmFn- reaction kinetics, including oxidation reactions. Rate constants and product ion distributions at 298 K are reported for over 60 reactions, and reactivity trends are discussed.