Strains representing the taxa Curtobacterium, Brevibacterium saperdae, B. testaceum, Corynebacterium betae, Cor. nebraskense and Cor.oortii were degraded by acid methanolysis and the non-hydroxylated fatty acid esters released were examined by thin-layer and gasliquid chromatography. The major fatty acids in all strains were 12-methyltetradecanoic (anteiso C15) and 14-methylhexadecanoic (anteiso C17) acids which occurred together with other anteiso, iso and straight-chain acids. Polar lipids of the test strains were examined by two-dimensional thin-layer chromatography. All organisms possessed very characteristic polar lipid patterns consisting of diphosphatidylglycerol, phosphatidylglycerol and a number of uncharacterized glycolipids. The menaquinone components of the test strains facilitated their division into two groups containing, respectively, nine isoprene units (viz. Curtobacterium citreum, Curt, luteum, Corynebacterium betae, Cor. flaccumfaciens, Cor. oortii, Cor. poinsettiae and Cor. nebraskense) and eleven and twelve isoprene units (viz. Brevibacterium saperdae, B. testaceum). The results of the present study indicate that the genus Curtobacterium as presently recognized is a heterogeneous taxon containing two distinct centres of variation.