New antibiotics, mycoplanecins, were found in the culture broth of an actinomycete identified as Actinoplanes awajinensis subsp. mycoplanecinus subsp. nov. Mycoplanecin complex was extracted with organic solvents both from the culture filtrate and mycelium and purified by column chromatography on silica gel and Florisil. Mycoplanecin A, a major component, was separated by high performance liquid chromatography on Prep PAK-500/C18 column. The physico-chemical characterization revealed that mycoplanecin A was a new cyclic peptide antibiotic. Mycoplanecins exhibited strong activities primarily against mycobacteria and related microorganisms.