21 new halogenated 3-(4-alkylphenyl)-1,3-benzoxazine-2,4-(3H)- diones were synthesized; all the compounds were screened in vitro against three different strains of Mycobacterium; 6-bromo-3-(4-butylphenyl)-1,3-benzoxazine-2,4-(3H)-dione proved to be most active compound of the series