Des(diserylglycyl)ferrirhodin, DDF, a novel ferric siderophore isolated from Aspergillus ochraceous, was identified as hfL-[hfL-[N5-hydroxy-N5-(cis-5-hydroxy-3-methyl-l-oxo-2-pentenyl)-~-ornithyl]-N5-hydroxy-N5-(cis-5 hydroxy-3-methyl-l-oxo-2-pentenyl)-~-ornithyl]-~-hydroxy-~-(cis-5-hydroxy-3-methyl-l-oxo-2-pentenyl)-~ ornithine. Evidence for the structure of the siderophore was obtained from 'H and 13C NMR of its deferri and gallium(III) complex forms, from synthesis of its N-acetyl and methyl ester derivatives, and from degradation studies. This is the first fungal siderophore with a linear tripeptide backbone.