Tuberculin Skin Test (TST) had been used in the diagnosis of Latent Tuberculosis Infections (LTBI) for about 100 years and has many disadvantages. In recent years there has been an increase in the number of investigations on new tests to be used instead of TST. With the better understanding of the genomic structure of Mycobacterium tuberculosis, specific antigens for this genome have been detected. Activated T cells from individuals infected with M. tuberculosis secrete Interferon Gamma (IFN-γ) when they are exposed in vitro to specific antigens. In recent years, new tests evaluating T cells secreting IFN-γ and IFN-γ secretion have been developed which are more specific in the diagnosis of M. tuberculosis infections. In this review, the role of IFN-γ assays in the diagnosis of tuberculosis infection and disease was evaluated in the light of current literature.