Alloys of Zn-Co were deposited from sulphate electrolytes containing various additives to study their influence on the anomalous behaviour of the reactions. The effects of antimony, germanium and arsenic on the Zn-Co alloy composition and structure were examined. The results showed that the composition and structure of Zn-Co alloys deposited could be dramatically changed by antimony, and to a lesser extent by germanium and arsenic. A concentration of Sb(III) as low as 5 mg dm-3 increased the cobalt content by a factor of approximately 3; however, the deposit morphology was very dendritic. Germanium additions nearly doubled the cobalt content and the morphology was somewhat improved. The effects of process parameters such as agitation and current density in the presence of the additives were also investigated.