After years of decline, the incidence of reported tuberculosis cases in France rose from 1991 to 1993, increasing from 14.7 cases per 100,000 inhabitants to 16.8. This incidence declined again between 1993 and 1995, falling to 14.9. However, significant regional disparities remain. The Île-de-France region remains the most affected, with an incidence rate of 35.7 cases per 100,000 inhabitants. This region’s unique epidemiological situation led us to assess, in 1995, tuberculosis cases belonging to the same transmission chain and to identify the associated risk factors. The identification of homelessness as a major risk factor associated with belonging to a tuberculosis transmission cluster highlights the vulnerability of the economically disadvantaged population to tuberculosis, both as an infection and as a disease. (adapted from the text).