Two antigens from Babesia bovis,12D3 and 11C5, were expressed and purified as recombinant proteins in Escherichia coli and used to vaccinate groups of six Babesia-susceptible cattle. These were subsequently challenged with a highly virulent strain of B. bovis. All cattle showed symptoms of disease and most required treatment. Cattle vaccination groups receiving either 12D3 or 11C5 or a combination of both, reduced parasitaemia by approximately fourfold and a number of individual animals appeared to control the parasite infection. Control of parasites correlated with high monocyte numbers late in infection. The results thus confirm the potential usefulness of both antigens but also demonstrate the limitations of current formulations.