Semiempirical (MNDO, AM1 and PM3) and ab initio (HF/3-21+G(d,p), MP2/3-21+G(d,p), HF/6-311+G(d,p) and MP2/6-311+G(d,p)) energy minimization and frequency calculations have been carried out on five hydrogen fluoride polymers, (HF)(n), n = 2, 3, 4, 5, and 6; on four polyfluorohydrogenate(1-) anions, HnFn+1-, n = 1, 2, 3, and 4; and on two polyfluorohydrogen(I) cations, Hn+1Fn+ n = 1 and 2. From the results, Delta G degrees, Delta H degrees, Delta S degrees values have been calculated for a number of reactions involving these species. The thermodynamic data are presented for 23 reactions using calculations at the MP2/6-311+G(d,p) level, along with a comparison of Delta G degrees values obtained from all seven molecular orbital methods.