A series of substituted azabischalcones Ia-Ip, monochalcone II and dihydroxyderivative III has been prepared and examined for their in vitro activity against Mycobacterium tuberculosis, Mycobacterium kansasii, Mycobacterium avium, Mycobacterium fortuitum as well as INH-resistant strains. Several compounds under study have the same activity as INH and greater than PAS, Contebene, Ethionamide. The results are summarized in Table 1. In the case of compound Ie, its in vivo activity was studied against M. tuberculosis as well (see Table 2). The toxicity of compounds under study is very low--2000 mg/kg/mouse.