Approximately one third of the world's population is infected with Mycobacterium tuberculosis,yet each year a small proportion of those individuals progress to an active disease state. Early identification and treatment of such individuals is essential to reduce transmission; however, genetic and immunological correlates of disease progression have not been well established in man. The murine model has been a central tool for the elucidation of protective immune mechanisms that are essential for controlling M. tuberculosis infection. Additionally, the study of inbred mice has revealed significant divergence in the susceptibility and disease progression of individual mouse strains to an infection with M.tuberculosis. The continued study of genetically disparate mouse strains has the potential to identify immune mechanisms that correlate with increasing susceptibility to tuberculosis. These mechanisms will be highly applicable to studies in man and assist in the early detection of individuals that are more vulnerable to the development of reactivation tuberculosis.