Ehrlichia ruminantium is an obligate intracellular bacterium that causes heartwater in ruminants and for which T-cellmediated immunity is believed to play an important role in protection. To better characterize protective cellular immunity E. ruminantium-specific IFN-[gamma] and IL-4 recall responses in major T-cell subsets were analysed by flow cytometry during immunization of goats with a killed vaccine and following a virulent challenge. The killed vaccine elicited both CD8+ and CD4+ subsets to produce cytoplasmic IFN-[gamma] in the absence of IL-4, thus indicating a biased Tl response. The relative capacity of CD8+ T-cells to produce IFN-[gamma] was significantly higher than CD4+ T-cells but the final contribution of both subsets was comparable. Circulating ER-specific CD4 and CD8 effectors substantially decreased in numbers after the booster injection and could not be detected in most animals during challenge, which warrants further investigation in immune compartments other than blood. Since IFN-[gamma] inhibits the growth of the pathogen in target cells, the information provided in this study on E. ruminantium-specific T1 responses will be valuable to develop cellular tools for the identification of potential protective antigens.