A low molecular weight hemorrhagic toxin, LMHT, was isolated from the venom of Trimeresurus flavoviridis from Yorojima using Q-Sepharose column chromatography. The purified hemorrhagic toxin was homogeneous by disc polyacrylamide gel electrophoresis at pH 8.3, and Ouchterlony immunodiffusion. LMHT has a molecular weight of 16,500 and possesses hemorrhagic activity. It did not show casein, azocasein, azoalbumin, or TAME (tosyl-L-arginine methyl ester hydrochloride) hydrolytic activities. Hemorrhagic activity was inhibited by EDTA, TEP (tetraethylenepentamine), p-APMSF(p-amidinophenylmethanesulfonylfluoride HCl), and N-bromosuccinimide. The minimum hemorrhagic dose of this hemorrhagic toxin was 7.1 microg/mouse. LMHT induced hydrolysis of the Aa and Bbeta chains of bovine fibrinogen.