Strain No. 41042, an actinomycete isolated from a soil sample, was found to produce 5-azacytidine and new antibiotics, mycoplanecins. Yellowish brown to yellowish orange color of colonies on agar media, formation of globose to subglobose sporangia bearing motile spores and presence of meso- and hydroxy-diaminopimelic acid and glycine in the cell wall ascribed this strain to genus Actinoplanes. From its morphological, cultural and physiological characteristics, this strain was determined to be a new subspecies of Actinoplanes awajinensis and designated as A. awajinensis subsp. mycoplanecinus subsp. nov. Production of mycoplanecins was carried out by conventional submerged culture: the highest antibiotic titer obtained was 145 micrograms/ml.