A new antibiotic, oryzoxymycin (C21H30N2O10, m. w. 470.47; λmax 285 mμ in 0.1N HCl; [α]D +240°, c=1, in H2O), inhibiting Xanthomonas oryzae was isolated. The producing strain was classified as Streptomyces venezuelae var. oryzoxymyceticus. Production, isolation, purification and physico-chemical properties of this antibiotic are described. During the course of screening for antibiotics active against X. oryzae in vitro and in green house tests, a potent broth was obtained from a culture of an Actinomycetes isolated from soil. The active component was purified, differentiated from all known anti-xanthomonas antibiotics, and was named oryzoxymycin. It inhibited the growth of X. oryzae in vitro at 1-2 mcg/ml but was not effective against bacterial leaf blight in a pot test, when applied in solution at 1,000 mcg/ml.