During the course of our work on the synthesis and screening of new drugs for tuberculosis, we have identified N1-(4-acetamido phenyl)-N4-(2-nitro benzylidene) semicarbazone (1b), which inhibited in vitro Mycobacterium tuberculosis H(37)Rv; 100% inhibition at 1.56 microg/mL. This paper is first of its kind in which aryl semicarbazones are reported to possess antimycobacterials potency greater than p-aminosalicylic acid, ethionamide, ethambutol, ciprofloxacin and kanamycin.