The human immunodeficiency virus (HIV) infection has both a direct and an indirect effect on the incidence of tuberculosis. The direct effect is due to the increased number of cases among HIV-infected individuals because of their enhanced susceptibility to the disease. The indirect effect is increased transmission of Mycobacterium tuberculosis infection in a community with high levels of dual infection, as a consequence of infectious cases occurring in HIV-infected persons. The risk of infection by M. tuberculosis in the population will then increase, as will the number of tuberculosis cases in the general population. According to the World Health Organization, over 4 million people are estimated to be dually infected with HIV and M. tuberculosis world-wide. In 1990, it was estimated that 300,000 new TB cases (4% of total new cases) were attributable to HIV infection; around 1.4 million cases are expected per year by 2000 (equivalent to about 14% of expected cases), thus increasing the reservoir of tuberculosis patients capable of transmitting the infection to others, and increasing the burden on the already overstretched National Tuberculosis Control Programmes, especially in resource-poor countries. This paper is a review of methods suggested to quantify the effect of the interaction between HIV infection and tuberculosis at population level, and more particularly the effect of HIV on the risk of tuberculosis infection.