Tuberculosis still a major public health problem despite effective therapy and good eradiction programs are availabile. The aim of this study was to reveal the influence of the BCG vaccine on TST results, to see the size of PPD induration is effected by BCG and which of the received vaccines gives the greatest effect. The study included children who were in the years 2009/2010. and 2010/2011. in the 7th grade elementary school. Their PPD reactions were the key to the discovery of BCG effects, vaccines that they have received as nonreactors or not received within the official immunization schedule during lifetime. BCG vaccine has a variable effect on TST. It has been shown that in non-vaccinated children tuberculin reactions slightly increase or they were approximately similar and slightly higher than in the vaccinated children. The intensitiy of PPD reactions increased during the years because of the different risk factors in children, but further booster vaccination of nonreactors against tuberculosis had effects in increasing the size of the PPD reaction and thus masquerading LTBI. The most largest and excellent results in effectivness are in children who recived the vaccine is in the earliest age.We need to invest a lot of effort on discovering evan better vaccines that will have no effect on TST but will provide an effective and longlasting protection against TB.