Amauromine is a new alkaloid with vasodilating activity obtained from the culture broth of Amauroaucus sp. No.6237. Its molecular formula was determined to be C32H35N46N4O2 on the basis of elementary analysis and high resolution mass spectroscopic measurement. It has low toxicity in mice. In the course of our screening program for new vasodilators among microbial metabolites using superfusion technique, a strain of Amauroaucus sp. No.6237 was found to produce the highly potent new vasodilator, designated amauromine. In this paper, the taxonomy of the producing organism, fermentation, isolation procedures, chemical and biological properties of amauromine are described.