A series of 11 alpha,omega-diaminoalkanes, (H(2)N(CH(2))(n)NH(2), n=2-12) have been evaluated for their in vitro antibacterial activity against Mycobacterium tuberculosis H37Rv. Compounds, (H(2)N(CH(2))(n)NH(2), n=9-12), exhibited a very good activities in the range 2.50-3.12 microg/mL, which can be compared with that of the first line drug, ethambutol (3.12 microg/mL). These results and a preliminary QSAR study can be considered an important start point for the rational design of new leads for anti-TB compounds.