We present measurements of ballistic magnetoresistance in nanocontacts grown by electrodeposition of Ni microclusters on magnetic thin films covered by aluminum oxide layers, using a technique proposed by Schad et al. [D. Allen, R. Schad, G. Zangari, I. Zana, D. Yang, M. C. Tondra, and D. Wang, J. Vac. Sci. Technol. A. 18, 1830 (2000); Appl. Phys. Lett. 76, 407 (2000); D. Allen, R. Schad, G. Zangari, I. Zana, D. Yang, M. C. Tondra, D. Wang, and D. Reed, J. Appl. Phys. 89, 6662 (2001)]. The measurements are made on single Ni clusters in contact with a Ni and Co thin film. We measure the magnetoresistance and observe the relaxation of the magnetization and electrical resistance as a function of time. The clusters are electrodeposited under several different experimental conditions. Some are deposited randomly on an unpatterned film and some through various patterned photoresists that control the location at which the cluster is grown. The typical contact size is estimated from the electrical resistance to be 10–30 nm. Ballistic magnetoresistance values up to 14% are obtained in these first experiments. © 2001 American Institute of Physics.