Co/Ni multilayer thin films with a constant Co thickness of 2.2 nm, Ni thickness ranging from 0.5 to 5.0 nm, and a total of 20 bilayers were fabricated using dc magnetron sputtering. These multilayers show a steep magnetoresistance (MR) change with low saturation magnetic field, in‐plane uniaxial anisotropic properties, and an especially large magnetoresistance change between magnetic fieldHapplied parallel and perpendicular to the in‐plane easy axis. ForHparallel to the multilayer easy axis andHat 45° to the currentI, a MR ratio of 15% with a FWHM of 13 Oe was obtained. While forHperpendicular to the easy axis and at 45° toI, a MR ratio of 19.1% with a FWHM of 34 Oe was obtained. The former implies a MR sensitivity of 1.15%/Oe, while the sensitivity of the latter is 0.56%/Oe. All the peaks of the MR curve appeared at the coercive fieldHcof the multilayers. The most important characteristics of the MR change were a sharp increase in resistance followed by a very steep decrease with increasingH. These Co/Ni multilayers are promising candidates for magnetic storage and sensor technology. ©1996 American Institute of Physics.