Magnetoimpedance in as‐cast, nonmagnetostrictive CoFeBSi amorphous ferromagnetic wires, submitted to an ac electric current of 5 mA in the frequency range 100 Hz–100 kHz, is analyzed in terms of equivalent circuits. It is shown that the equivalent circuit representing the wire frequency behavior can be approximated by a parallelLpRparrangement with elementsRsandLsin series;LpandRpare associated with circumferential domain wall permeability and wall damping, respectively;Lsis related to the circumferential rotational permeability of the wire, andRsaccounts for the dc resistance in the circuit. When the wire is submitted to a longitudinal dc field high enough to approach saturation (Hdc=3600 A/m), the circuit becomes simply a seriesRsLscircuit. The various contributions from basic magnetization processes to magnetoimpedance are discussed, as well as deviations from this idealized model. ©1995 American Institute of Physics.