A streptothricin-like antibiotic, A-269A (referred to as A-269A hereafter) was isolated from the culture broth of Streptomyces sp., strain No. A-269. In this paper, the characterization of the producer, and the production, isolation, physico-chemical properties and biological properties of A-269A are reported. The structure of the antibiotic was also examined by 1H NMR, 13C NMR and fast atom bombardment mass spectra studies. From the spectroscopic data, A-269A was assumed to be a mixture of antibiotic LL-BL 136 and an isomeric compound in which the carbamoyl group is substituted on C-12' hydroxyl instead of C-10 hydroxyl.