Some higher alkyl ethers of o-aminophenol were prepared and antibacterial actions of their hydrochlorides against human type tubercle bacilli were tested in vitro (Kirchner medium) and by S. C. C. method. Compounds synthesized were ethers of methyl, ethyl, butyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl and benzyl. As long as the alkyl group in these ethers are straight-chain, saturated carbons of even number, there is a definite relationship between the length of the alkyl chain and the antibacterial action, the latter increasing with the increase of the number of carbon atoms. The maximum action (1:128, 000, by S. C. C. method) was found with an alkyl chain of 12 carbons, increase of carbon atoms above that resulting in the decrease of antibacterial action.