This study was undertaken to elucidate the structure of choline glycerophospholipids (CGPs) in the marine annelid Marphysa sanguinea. By application of recycling HPLC and other chromatographic techniques, ten CGPs were isolated in pure state, including six lyso platelet-activating factors (lyso PAFs), two β-lysophosphatidylcholines, and two 1-alkyl-2-acyl-sn-glycero-3-phosphocholines. The two 1-alkyl-2-acyl derivatives were identified as 1-hexadecyl-2-arachidonoyl-sn-glycero-3-phosphocholine and 1-hexadecyl-2-eicosapentaenoyl-sn-glycero-3-phosphocholine, which comprised 28% of the alkylacyl CGP fraction and are considered the main components of PAF-like lipid (stored precursor form of PAF) in this material.