Aureothricin is an antibiotic first described by Umezawa and co-workers in Japan in 1949. Resurgent interest in this class of microbial metabolites was stimulated by the discovery of their selective antitumor activity. Aureothricin is a more hydrophobic analogue of thiolutin, but has received only limited attention. Members of this class, notably thiolutin, are potent inhibitors of bacterial and yeast RNA polymerases, inhibitors of mannan and glucan formation in fungi, and inhibitors of tumor-cell induced angiogenesis in vivo.