The complex structure of the cell wall of Mycobacterium tuberculosis clearly contributes to the outcome of the dialogue between this pathogen and its host. The effects of mutations in cell wall components are likely to be quite complex, as individual components of the wall could have indirect effects that extend well beyond the physical integrity of the wall itself. Affected processes include the surface exposure or secretion of the many lipid, glycolipid and proteinaceous molecules that can interact directly with components of the host cell.