We have previously reported on a new antibiotic, FR-900482, possessing a hydroxylamine function whose hydroxyl group exists as a hemiketal moiety, an aziridine function and a carbamoyloxymethyl group in the structure1>2). In addition to producing FR-900482, Streptomyces sandaensis No. 6897 also biosynthesizes FR-66979 (Fig. 1), a dihydro derivative of FR-900482^. In this paper, the isolation, physicochemical properties and biological activities of FR-66979 are reported.