Utilization of the dietary sterols by prawn, Penaeus japonicus, was studied. After 30 day-feeding on the diets containing only cholesterol, ergosterol, stigmasterol, and β-sitosterol, the content and composition of sterols in the tissues of the prawn were analyzed. In the prawn fed on the sterol-supplemented diets, the sterol content of the body tissues was similar to that of the prawn before feeding though in the prawn fed on the sterolfree diet, the sterol content decreased. In the prawn fed on several sterol-supplemented diets, 96-99% of the sterol content was composed of cholesterol. From these results, it may be assumed that the dietary ergosterol, stigmasterol, and β-sitosterol were digested by the prawn, and converted to cholesterol.