On supplementation of fermentations of Streptomyces griseochromogenes, an organism that produces the anti-fungal antibiotic blasticidin S (BS), with L-arginine hydroxamate in order to block the de nouo biosynthesis of Larginine, an essential precursor for BS, the accumulation of five new metabolites resulted. These new metabolites were purified by ion exchange chromatography and HPLC, and were characterized by NMR and mass spectroscopy and by chemical degradation. Two are normally very minor metabolites of S. griseochromogenes, while the other three are derived in part from the inhibitor that had been added to the fermentation.