The isolation of chitinovorins A, B and C from the culture broth of Flavobacterium chitinovorum sp. nov. PB-5016 has been reported previously'). After that, seven additional chitinovorins-producing strains which all belong to the genus Flavobacterium were isolated in our searching studies for new ƒÀ-lactam antibiotics from bacteria. One of them, Flavobacterium sp. PB-5246, was found to produce a more strongly basic antibiotic named chitinovorin D together with chitinovorins A, B and C. In this paper, the isolation and characterization of chitinovorin D are presented (hereafter, chitinovorin is abbreviated as CTV).