Abstract: From the venom of O.hannah,seventeen fractions had been isolated by column chromatography on CM-sephadex C25 as previously described.Among the seventeen fractions,fractions 7,8,9 and 11 produced an antidepolarizing neuromuscular block.But they were contaminated with phosphomonoesterase,phosphodiesterase,5-nucleotidase and ribonuclease.After re-chromatography on CM32 and gel filtration on sephadex G50,7-A,8-B,9 and 11 were confirmed to be homogenous by polyacrylamide gel electrophoresis.That si to say,they were free from phosphomonoesterase,etc.We determined the amino acid compositions and N-terminal groups of the four purified fractions.The experiment on rat phrenicdiaphragm and denerved rat diaphragm preparations in vitro and the determination of amino acid compositions suggested that O.hannah venom contained both long neurotoxins and thort noes.The site of action was found to be in the postsynapse instead of the in the presynapse.