Tetramethylammonium(TMA, tetramine) is a toxic quaternary ammonium compound, consisting of four methyl groups attached to a central nitrogen atom. TMA has been detected in a number of marine organism that are eaten by humans. In the past, most cases of TMA intoxication have occurred through eating seafood containing TMA, such as carnivorous gastropods. Nowadays, TMA hydroxide(TMAH) that decomposes to produce TMA is used widely in the manufacture of semiconductors and liquid crystal displays (LCDs). As a result, the case of TMA intoxication is increasing. TMA acts directly on nicotinic and muscarinic receptors that are responsible for depolarization and, at high doses, blockage of depolarization. TMA may cause nausea, vomiting, headache, impaired vision, temporary blindness, salivation, lacrimation, fasciculation and convulsion and motor paralysis. The symptoms of TMA intoxication generally are mild and transient because of rapid elimination of TMA from the body. However, in severe cases, paralysis of the respiratory muscles can occur and this causes death. In this study, we analyzed TMA in femoral blood, heart blood and gastric contents of victim. The concentrations of TMA in femoral blood and heart blood were 7.95 mg/L and 13.1 mg/L, respectively. This case can be considered as a good reference when studying the relationship between TMA-induced death and blood concentration.