Total lipids from hepatopancreas of the horseshoe crabs, Tachypleus gigas and Carcinoscorpius rotundicauda, obtained in 7.6 and 3.3% wet weight respective yields, were fractionated by various chromatographic techniques and identified by gas-liquid chromatography and spectroscopic methods. Fatty acid-containing lipids were rich in 16:0 (8.0-25%), 18:1ω9 (6.9-22%) and 18:2ω6 (6.8-18.5%); appreciable amounts of 16:1ω7, 18:3ω3, 20:5ω3 and 22:6ω3 were also present. The level of 26:0 in the hydrocarbon fractions was unusually high (64 and 68%). Carbon chain lengths of major wax esters were 44, 46 and 48 for T. gigas and 38, 40 and 42 for C. rotundicauda. 1-O-Alkyl diglycerides were 7.2 and 9.1% of the total lipids in the two species and contained 14:0(20%), 16:0(60%) and 18:0(20%) alkyl chains along with a relatively higher percentage (32-35%) of saturated fatty acids. High levels of cholesterol (>50% of total sterol) in the free and combined state were encountered in both samples, phospholipid contents being 40 and 35%, respectively, and contained highest levels of unsaturated fatty acids. © 1989 American Oil Chemists' Society.