Teichomycin (teicoplanin) was found to be a mixture of five closely related components of similar polarity, designated T-A2-1, 2, 3, 4 and 5 and of one more polar component, designated T-A3. The separation of the single components was achieved by reverse phase partition chromatography and their physico-chemical and biological properties were compared. The results show that 1) the five major components have the same molecular size of about 1,900; 2) they contain the same ionization function, i.e., a carboxyl group and an amino group which form a zwitterion, and four phenolic groups; 3) they differ in a side aliphatic chain. The component T-A3 is not described.