The antibiotic d-cycloserine inhibits the synthesis of the wax D peptidoglycolipid in cells of the H37Ra strain of Mycobacterium tuberculosis. This inhibition occurs at a lower concentration of the drug than that required for the inhibition of growth. The inhibition is completely reversed by d-alanine. An arabino-galactan-galactosamine-(diaminopimelic acid)-mycolate accumulates in H37Ra cells exposed to the antibiotic. The chemical and functional group analyses of this lipid suggests it to be a possible precursor to the synthesis of wax D.