The magnetoresistance of single Co nanowires of various widths is investigated at low temperatures applying magnetic fields mu(0)H up to 4.5T. The in-plane longitudinal magnetoresistance shows pronounced features at coercive fields H,, explained by the anisotropic magnetoresistance indicating the magnetization reversal process. Monte Carlo simulations present the magnetization distribution during the reversal process, revealing different mechanisms depending on the wire width. (C) 2002 Elsevier Science B.V. All rights reserved.