Ceramide aminoethylphosphonate was isolated from the shellfish, AGEMAKI, Sinonovacula constricta. The compound was purified through a combination of mild alkaline hydrolysis of the total lipids, QAE-Sephadex-A25 column chromatography and two dimensional thin layer chromatography. The infrared spectrum showed an absorption band at 1180cm-1 due to a C-P bond, and was essentially identical with that of the standard ceramide aminoethylphosphonate. Upon hydrolysis of the substance with a strong acid, neither a change in its chromatographic behavior nor liberation of inorganic phosphate was observed. The stability of the compound as to acid hydrolysis suggested the presence of a C-P bond. On comparison with the synthetic compound, the aqueous hydrolysis product was found to behave like 2-aminoethylphosphonic acid on thin layer chromatography. The predominant fatty acids were palmitic acid and stearic acid. The results obtained suggest that a person may ingest and absorb 2-aminoethylphosphonic acid, through the food chain, on the consumption of edible shellfish.