The structure of methyldifluoroamine, CH3NF2, was determined by gas-phase electron diffraction augmented by rotational constants from microwave spectroscopy taken from the literature and by results from molecular orbital calculations. The structural results are consistent with C-s symmetry for a molecule with staggered bonds. The experimental bond distances and bond angles (r(alpha)(o)/r(g)) and angle(alpha)), with estimated 2 sigma uncertainties are C-H = 1.104/1.124(5) Angstrom (average value), N-F = 1.406/1.408(2) Angstrom, C-N = 1.467/1.469(6) Angstrom, C-N-F = 104.1(2)degrees, F-N-F = 101.7(2)degrees, N-C-H-anti = 109.9(11)degrees N-C-H-gauche = 106.5(10)degrees H-gauche -C-H-gauche = 110.6(28)degrees; the subscripts indicate orientation with respect to the nitrogen lone pair. A scaled quantum-mechanical (SQM) quadratic vibrational force field was evaluated by symmetrizing the quantum-mechanical (MP2/6-311++G(d,p)) Cartesian force constants and scaling the results to fit observed infrared wavenumbers from the literature. The N-F; stretching force constants for the other fluoroamines NF3 and (CH3)(2)NF were also determined in a similar fashion. Contrary to an earlier report, the values were found to increase with decreasing bond length consistent with Badger＇s rule.