Food poisoning due to ingestion of a puffer fish occurred in Nagasaki 
Prefecture, Japan, in October 2008, causing neurotoxic symptoms similar to those 
of tetrodotoxin (TTX) poisoning. In the present study, we identified the 
species, toxicity, and toxins using the remaining samples of the causative 
puffer fish. The puffer fish was identified as smooth-backed blowfish 
Lagocephalus inermis by nucleotide sequence analysis of the 16S rRNA and 
cytochrome b gene fragments of muscle mitochondrial DNA. The residual liver 
sample showed toxicity as high as 1,230 mouse unit (MU)/g by bioassay and TTX 
was detected by liquid chromatography/mass spectrometry analysis. We therefore 
concluded that the food poisoning was due to TTX caused by consumption of the 
toxic liver of L. inermis. This is the first report that the liver of L. inermis 
caught in Japanese waters is strongly toxic, with levels exceeding 1,000 MU/g. 
In this context, we re-examined the toxicity of L. inermis collected off the 
coast of Japan. Of 13 specimens assayed, 12 were toxic, although the toxicity 
varied markedly among individuals and tissues. Because the intestine and ovary 
of L. inermis have been considered non-toxic, it is particularly noteworthy that 
these organs were determined to be toxic, with a maximum toxicity of 43.6 MU/g 
and 10.0 MU/g, respectively. Furthermore, kidney, gallbladder, and spleen, whose 
toxicity has been unknown, were frequently found to be weakly toxic with levels 
ranging from 10 to 99 MU/g. Therefore, further study is needed to re-examine the 
toxicity of smooth-backed blowfish L. inermis in the coastal waters of Japan.