We have measured the magnetoimpedance of ferromagnetic wires placed as internal conductors in shorted coaxial lines. We have also modeled the impedance by simultaneously solving Maxwell’s equations and the Landau–Lifshitz equation of motion for the magnetization in a cylindrical magnetic conductor under the appropriate boundary conditions. The permeability of Ni45Co25Fe6Si9B13Mn2 amorphous wires, deduced from the impedance, is compared with the model on plots of the imaginary part of the permeability versus the real part, with the dc magnetic field as implicit parameter. This approach emphasizes the region of ferromagnetic resonance and facilitates the investigation of the permeability locus. A number of intrinsic parameters of the magnetic wire, such as the exchange constant, the damping constant, and the gyromagnetic ratio, have been evaluated.