The guinea pig is a very useful animal model for evaluating new tuberculosis candidate vaccines. In addition to established methods for bacterial load determinations, new technologies are emerging that allow us to specifically evaluate effects of vaccines on the pathology of the disease process and the expression by the host of cell mediated immunity. Limitations to the model include housing and related costs, which often contribute to issue with study design and adequate statistical power, and the use of laboratory strains of Mycobacterium tuberculosis which lack the high virulence and immune evasion properties of newly emerging clinical isolates.