In the development of highly sensitive bio-magnetic field sensors, extremely magnetically soft sensing elements are essential. Cold-drawn wires have been known to possess high uniformity in material composition and microstructure. In this study, Ni80Fe20/Cu composite microwires, with an overall diameter of 96 mu m and a thickness ratio Ni80Fe20/Cu/Ni80Fe20 of 1:4:1, were developed through the process of cold-drawing. The results showed that the ratio of the NiFe layer thickness to the copper core remained unchanged throughout the drawing process, the cold-drawn wire has a longitudinal anisotropy, and the permeability of permalloy in the cold-drawn wire can be enhanced by increasing the temperature in annealing. (c) 2005 Elsevier B.V. All rights reserved.