Various organs of the butterfly fish Chaetodon trifascialis, which has been reported to feed exclusively on coral polyps, were analyzed for their content of lipid and of the wax cetyl palmitate which has been found to occur in various corals. Cetyl palmitate was isolated from stomachs containing food. The total lipids accounted for 12% of dry weight of stomachs and contents, with cetyl palmitate making up 30% of total lipids. Two stomachs contained a total of 315 mg of cetyl palmitate. No significant amounts of the wax were found in heads, ovaries, swim bladders and intestines of the fish, indicating an exogenous source of the cetyl palmitate present in the stomach. This finding supports the view that the butterfly fish feeds on corals, which contain cetyl palmitate. The butterfly fish does not appear to store wax.