A total of 70 specimens of the trumpet shell Charonia sauliae ("boshubora") were collected at eight places in Kagoshima Prefecture in October 1983 through May 1984. Their digestive glands were removed and examined for toxicity by the assay method of tetrodotoxin (TTX). Remarkable regional and individual variations in toxicity were noted. On the whole, the ratio of toxic to total specimens was 43%, the highest and average toxicity scores being 1,670 and 81 MU/g digestive gland, respectively. Trumpet shell toxin was identified as TTX from thin-layer chromatographic and electrophoretic behaviors, along with GC-mass spectrum. Small pieces of a starfish Astropecten scoparius which were found in the digestive canal of some specimens showed a toxicity of 8-30 MU/g, suggesting the involvement of this starfish in toxification of the trumpet shell.