Human antimycobacterial immunity is a critical component of tuberculosis (TB) pathogenesis that is often used to infer the presence of TB infection. We report high heritability (>50%) for in vitro secretion of tumor necrosis factor alpha and interferon gamma (IFN-gamma), and the frequency of antigen-specific IFN-gamma(+)CD4(+) and IFN-gamma(+)CD8(+) cells in the response of whole blood to mycobacterial challenge. In principal component analysis, the first 3 components explain 78% of the overall variance consistent with the effect of pleiotropic regulatory genes of human antimycobacterial immunity. These results directly demonstrate the pivotal role played by host genetics in quantitative measures of antimycobacterial immunity underlying immune diagnosis of TB infection.