Considering the ongoing difficulty with the interpretation of the tuberculin skin test and the importance of a correct interpretation of each situation in order to benefit from treatment, a lot of expectations are placed in the new Gamma Interferon blood tests. The aim of this article is to recall the basic principles of these tests and to review the evidence of their utility in paediatrics. In children, although the evidence is still insufficient, the blood tests can be useful in combination with the tuberculin skin test.