Polyoxin N, a new active component of the polyoxins, has been isolated from the culture broth of Streptomyces piomogenus . On the basis of degradative study and spectral analysis, the structure, 1-[5′-(5″-O-carbamoyl-2″-amino-2″-deoxy-L-xylonyl)amino-5′-deoxy-D-allofuranosyl uronic acid]-3-formyl-4-hydroxypyrazole (1), has been proposed for this antibiotic. Unlike other polyoxins, it has a pyrazole ring system as a nucleobase.