Chemical investigation of gorgonians has been intense and a large number of terpenoid and acetate derived metabolites have been discovered'. Several novel sterols, of which the Csc sterol gorgosterol (1)2 is the best known, have been reported from gorgonians. We now describe the isolation and structural elucidation of hippurin-1 (2) from rsis hippuris, a common gorgonian found on the Great Barrier Reef. Percolation of the milled freeze-dried organism with cold dichloromethane gave a 1.7% extract which was partitioned between petroleum ether and 95% methanol. Evaporation of the methanol layer gave a syrup representing half of the original extract. Chromatography of this mixture on silica gel using a dichloromethane-ethyl acetate gradient gave, in order of elution, a sterol related to (2) for which we propose the name hippurin-2 (3%), gorgosterol (1) (1.3%), hippurin-1 (2) (20%) and an orange.pigment (0.6%), identified as peridinin (3)3. Hippurin-1 crystallised from diethyl ether-petroleum ether as small rosettes4. The formula Cs0H4s07 was established by elemental analysis and high resolution mass spectral data on the first fragment peak at 505 a.m.u. (Mt -15). The 'H n.m.r. spectrum of (2) indicated the presence of the grouping -CH2-CH(OAc)-CH(OH)-CH2 (62.04, 3H,s; 44.97, lH,m, k/h/i 16 Hz ; coupled to a signal at 64.03, lH,m, Wh/z 7Hz). The data suggested that the acetoxyl group was equatorial and the hydroxyl group was axial. Two further -CH-O-signals were centred at 64.25.