Cobalt + nickel alloys were electrodeposited on different base-silicon substrates since these alloys are interesting for several magnetic device applications. Acid chloride baths were used to obtain magnetic cobalt + nickel layers directly over silicon surfaces, tantalum silicide or metallic seed-layers. Although the initial stages of nucleation were influenced by the kind of substrate, in all substrates nucleation and three-dimensional growth evolving to compact, fine-grained and homogeneous deposition, took place. Preferential deposition of cobalt and anomalous codeposition occurred. Different compositions of the alloy were obtained, as is normal with a solid-solution formation. The cobalt content in the deposit rose with increase in both cobalt(II) and saccharin concentrations and fell with decrease in the applied potential or current density.