The complete general harmonic force field of methyl flouride was recalculated using the most recent literature frequency, Coriolis zeta and centrifugal distortion data for (CH3F)-C-12, (CH3F)-C-13, (CD3F)-C-12, (CHD2F)-C-12 and (CH2DF)-C-12. The anharmonic corrections applied to the observed frequency data and the adopted molecular geometry are considered to be more realistic than those used hitherto. There is excellent overall agreement between the fitted force constants and the highest quality ab initio force field currently available.