Mutational biosynthesis has been shown to be a valuable technique for preparing new antibiotics. Recently, several groups have reported an isolation of 2-deoxystreptamine (DOS) idiotrophic mutants from various aminoglycoside-producing organisms and a preparation of new aminoglycoside antibiotics using this technique. Micromonospora sagamiensis was isolated by NARA et al. as a producer of sagamicin, a novel broad spectrum aminoglycoside antibiotic. In the present investigation, the authors attempted to utilize the DOS idiotrophic mutants for preparation of new mutasynthetic antibiotics. When streptamine, a structural analog of DOS, was fed to the mutants, a new antibiotic, 2-hydroxysagamicin, was produced. In this communication, isolation, identification and biological properties of the 2-hydroxysagamicin are described.