Abstract: Food paralytic poisoning incident was detected in the gastropod Nassariidae Niotha clathrata and Zeuxis scalaris occurred in December 2012 in Kaohsiung, Taiwan. The toxin was purified from each remain of cooked gastropod and victim tissues by ultrafiltration using a YM-3 membrane, followed by C18 cartridge column purification. Based on analyses by LC-MS/MS, the causative agent of gastropod food poisoning was identified as tetrodotoxin. The toxicity of remain of cooked sample was 245 MU/g (1MU = 0.178 μg TTX) for N. clathrata and 203 MU/g for Z. scalaris. The blood and excrements of victim was shown to contain TTX of 0.13 and 0.18 μg/g, respectively. There was positive between results from LC-MS/MS and mouse bioassay in the causative gastropod. The LC-MS/MS method is suitable for rapid screening of TTX.