Co-Cu films showing magnetoresistance (MR) were obtained by electrodeposition and post-annealing of the samples. Homogeneous cobalt-copper electrodeposits were obtained from a sulfate-citrate bath at pH 5.3 using glass/Cr or Si/Ti/Ni substrates. These substrates are appropriate for direct measurement of the MR of the Co-Cu films. Annealing conditions were optimized to increase MR. Low deposition current densities (in the range 2.7-3.7 mA cm(-2)) were used to prepare deposits with 10-25% Co that had, after annealing, MR values around 6-8% (at 27 K). The microstructure resulting from annealing was analyzed by transmission electron microscopy and X-ray diffraction. (C) 2004 The Electrochemical Society.