Abstract The steryl ester and phospholipid fractions of the marine sponge Agelas conifera were isolated and analyzed. The fatty acyl components of the steryl ester and phospholipid fractions as determined by gas chromatography and gas chromatography/mass spectrometry were very similar and consisted of 56.8 and 62.7% of C 14 −C 20 acids (normal; branched, especially iso and anteiso ; and monounsaturated, particularly Δ 9 and Δ 11 acids) and of 43.1 and 35.5% of C 24 −C 26 acids (Δ 5,9 diunsaturated acids), respectively. The major constituent fatty acids detected were 13‐methyltetradecanoic, n ‐hexadecanoic, 10‐methylhexadecanoic, 11‐octadecenoic, 12‐methyloctadecanoic, 5,9‐pentacosadienoic and 5,9‐hexacosadienoic acids. The phospholipids isolated were identified as phosphatidylcholine (37%), phosphatidylserine (34%), phosphatidylethanolamine (16%) and phosphatidylinositol (11%). The distribution of fatty acids within the phospholipid classes was also determined.