To develop reagents for characterizing M. tuberculosis antigens we have produced eighteen new anti-tuberculosis monoclonal antibodies (Mabs). At least three of these Mabs react specifically with M. tuberculosis complex. As demonstrated by protease sensitivity assays, 17 of these Mabs reorganize tuberculosis proteins. Whole cell ELISA protocols using these Mabs have also shown that several of the Mabs recognize surface associated molecules. M. tuberculosis culture filtrate (CF) proteins are among the most immunogence antigens of the tubercle bacilli. Four of our Mabs react with CF antigens in ELISA and 2 Mabs recognize CF proteins in western blot assays. By utilizing Mab and a lambda gene expression library, we are currently isolating the gene that encode an immunogenic 50 kDa tuberculosis CF protein.