Investigation of the surface magnetization reversal and the magnetoimpedance (MI) effect have been performed in Co-rich glass-covered microwires with identical composition and different thickness of glass covering. The correlation between the mechanism of the surface magnetization reversal and the value of MI effect has been discovered. The Kerr effect study showed that the bias magnetic field induces shift of circular hysteresis loop. This shift could be considered as a characteristic feature of the high value of the MI ratio. (c) 2006 Elsevier B.V. All rights reserved.