Haloquinone, a new antibiotic produced by Streptomyces venezuelae ssp. xantlzophaeus (Lindenbein) strain Tu 2115, was isolated from the mycelium (pH 4.5) by extraction with methanol and chromatography on acid-treated silica gel. The new compound, molecular formula C1,H120~, has been isolated with respect to its activity against halobacteria; it also inhibits Gram-positive and to a smaller extent Gram-negative bacteria. The antibiotic has an effect on DNA synthesis.