Tuberculosis (TB) is a major global health problem. The BCG is an attenuated vaccine. Tuberculin test is used as a nonspecific TB vaccination indicator. This study was aimed to determine the efficacy of BCG vaccine through screening of healthy, vaccinated adults’ subjects in Khartoum. A total of one hundred (n=100) healthy and TB symptoms free participants were screened by manteaux test. The participants were involving 55 (55%) males and 45 (45%) female. All participants were over 20 years and most of them had a scar in their vaccination site. All participants were screened through injection of purified protein derivative PPD (only 0.1 mL) intra-dermally into their volar forearm then 48-72 post-injection their induration diameter was measured. The results showed that out one hundred (n=100) participants, only 39 (39%) were positive for Manteaux test (≥ 10 mm diameter), while 61 (61%) were negative (≥ 10 mm diameter). Among the 39 positives, 33 show reading between 10 mm to 15 mm and 6 of them show zone ≥ 15 mm. In the other hand 53 out of 61 tuberculin test negative participants showed no induration post PPD injection and the rest were shows reading zone between 5 to 9 mm. The result shows that among the 39 positive participants 23 (58.97%) were male while only 16 (41.03%) were female. The mean of zone reading among the positive participants is higher in male 13.96 ± 3.29 than female 13.81 ± 2.22. The study concluded that more than half of the participants were negative for tuberculin test and this may be interpreted by either the vaccine was invalid or their cell-mediated immunity against TB is reduced. The discrepancy in the zone reading means between male and female may be related to some physiological difference. Further studies with more sample size and by using a more advanced technique (IFNγ) should be done to clarify the results.