The present invention relates to Mycobacterium tuberculosis (M tuberculosis) proteins and immunologically active fragments (peptides or mimotope peptides) thereof. In particular, the invention relates to a group of M. tuberculosis proteins and peptides thereof that are both highly antigenic and characteristic of clinical strains of M. tuberculosis. Accordingly, the further relates to the use of these M. tuberculosis proteins or peptides in diagnosing, treating or preventing M. tuberculosis complex infection.