The demonstration of the existence of active efflux pumps in mycobacteria raises the question of whether or not these can increase in number and activity rendering wild-type mycobacteria increasingly resistant to a given antibiotic. This could be a mechanism by which mutated resistant strains become better fit to the selective environment. Mycobacterium tuberculosis genome analysis reveals several genes encoding putative drug efflux pumps. During the course of tuberculosis chemotherapy many of these pumps might play a role in the survival of the mycobacterial populations. Compounds capable of inactivating these pumps could improve anti-tuberculous therapeutics.