A47934, a novel glycopeptide-aglycone antibiotic, is produced by a strain of Streptomyces toyocaensis, NRRL 15009. A47934 is unique among reported glycopeptides in that it contains a sulfate ester. Like several other glycopeptides, the majority of the A47934 produced remained associated with the producing biomass, from which it could be released into aqueous media by alkalization. Antibiotic biosynthesis was depressed when initial levels of phosphate phosphorus in the medium exceeded the normal level of 35 micrograms/ml. Enrichment of the fermentation medium with tyrosine depressed A47934 yields while enrichment with p-hydroxyphenylglycine or p-hydroxyphenylglyoxylic acid stimulated antibiotic biosynthesis.