Two novel heptadecaglycoside antibiotics, saccharomicins A (1) and B (2), were isolated from a new species of Saccharothrix. Their structures were determined by a combination of chemical degradation and spectroscopic methods. Saccharomicin B (2) was identified as N-(m,p-dihydroxycinnamoyl) taurine p-O- [R-4-epi-vancosaminopyranosyl(1f4)-R-4-epi-vancosaminopyranosyl(1f4)-R-digitoxopyranosyl(1f4)-R-4-epi-vancosaminopyranosyl(1f4)-R-digitoxopyranosyl(1f3)-â-fucopyranosyl(1f4)-â-saccharosaminopyranosyl(1f4)-R-digitoxopyranosyl(1f3)]-[R-4-epi-vancosaminopyranosyl(1f4)]-â-fucopyranosyl(1f4)-âsaccharosaminopyranosyl(1f4)-R-rhamnopyranosyl(1f3)-â-fucopyranosyl(1f4)-â-saccharosaminopyranosyl(1f4)-â-fucopyranosyl(1f4)-â-saccharosaminopyranosyl(1f4)-â-2-sulfate-fucopyranoside. Saccharomicin A (1) differs from saccharomicin B (2) only in the 10th sugar residue, where R-digitoxopyranosyl(1f3) is replaced with R-rhamnopyranosyl(1f3). The novel amino sugar residue, designated saccharosamine, was identified by NMR spectroscopy and X-ray crystallography. Both saccharomicins A (1) and B (2) showed antimicrobial activity against Gram-positive bacteria.