To evaluate the variability of tuberculin skin test (TST), we did a prospective study in the pneumology unit of the teaching hospital at Point G and in the tuberculosis unit of the health district II at Bamako, Mali TST was applied two times to every patient more than 18 years old: at the beginning before the tuberculosis treatment (tst1) and after 2 months (tst2). For all 113 patients followed in both units, 41 were enrolled in this study (36, 2%). The mean age of patients was 37.9 years and 73.2% were male.(sex proportion was 2.72 for male). The different forms of Tuberculosis were: 63.4% of tuberculosis with smear positive(TSP); 7.3% of tuberculosis with smear negative(TSN); and 29,3% of disseminated tuberculosis. 22% of the patients were HIV positive. The tst1 was positive for 58.5% of the patients(11.11% of the HIV positive patients and 78.13% of the HIV negative). The diameter of indurations of the TST increased considerably during the treatment mainly with patients infected by HIV. The TST test can be an indicator of follow op for these patients who had less AFB most of time?