We have determined the components of the magnetoresistance tensor through fifth order in the magnetic direction cosines for four epitaxially grown iron films with thicknesses between 200 and 60 A˚ at 300, 77, and 4.2 K. We have also determined their magnetic anisotropy parameters from ferromagnetic resonance at 300 K. These phenomenological parameters provide an excellent description of the magnetic field dependence of the planar magnetoresistivity for electric current directed along the [001], [11¯0], and [11¯(2)1/2] directions and the applied fields necessary to produce spin flops.