Leprosy-derived corynebacteria (LDC) have been extensively studied over the past decade. A composite of their biological properties (cell morphology, staining reactions, cellular inclusions and guanine-plus-cytosine content of their deoxyribonucleic acid; 16 strains studied) and their chemical structures (peptidoglycan type, major cell wall polysaccharide, major glycolipid as well as characteristic mycolic acids) appears to define them as members of the genus Corynebacterium. In relation to other corynebacteria found in humans, including "JK corynebacteria", they seem to be distinct. They are here named Corynebacterium tuberculostearicum sp. nov. because they produce a 10-methyloctadecanoic (tuberculostearic) acid (8 strains studied). This and some of their other attributes are considered in relation to properties of leprosy bacilli and Mycobacterium leprae.