A variety of N-monoand N,N-dialkyI-N'-[4-azo(5,6,7,8-tetrahydro-l-naphthyl-and -2,3-xylyl)] alkylenediamines were synthesized by (1) coupling a diazotized aromatic or heterocyclic amine with the requisite N,N-dialkyl-N'-(5,6,7,8-tetrahydro-l-naphthylor -2,3-xylyl)alkylenediamine, (2) condensation of N-(3-bromopropyl)-516,7,8-tetrahydro-4-phenyIazo-l-naphthylamine with the appropriate amine, and (3) alkaline hydrolysis of the corresponding N-(ammoalkyl)-2,2,2-trifluoro-N-(5,6,7,8-tetrahydro-4-azo-l-naphthyl)acetamides. Potent in vitro antituberculosis activity among the N-monoand N,N-dialkyl-N'-[4-azo(5,6,7,8-tetrahydro-l-naphthyland -2,3-xylyl)] alkylenediamines is widespread, and 28 compounds exhibited a similar order of potency as isoniazid. However, activity against Mycobacterium tuberculosis H37Rv in mice is relatively specific, and strong effects were observed only among the l-(3-{ [5,6,7,8-tetrahydro-4-(phenylazo)-1-naphthyl] amino)propyl)piperidines (I) and l-(3-j [5,6,7,8-tetrahydro-4-(3-pyridylazo)-l-naphthyl] amino }propyl)piperidines (II). Four representative compounds among the latter types also showed definite suppressive antileprotic activity against M. lepraemurium in mice. Structure-activity relationships are discussed. also thank Dr.