Cytotoxic product(s), which are responsible for inducing the release of acetylcholinesterase-enriched vesicles from human erythrocytes and cell lysis, are generated when 1-saturated-2-polyunsaturated glycerophosphocholine was incubated with oxyhemoglobin (Itabe, H., Kobayashi, T. and Inoue, K. (1988) Biochim. Biophys. Acta 961, 13-21). To identify the products, a model compound, 1-O-octadecyl-2-linoleoylglycerophosphocholine was incubated with oxyhemoglobin. The oxidation products were isolated by both straight-phase and reverse-phase HPLC. The products, which were responsible for inducing erythrocyte membrane damage, were analyzed by secondary ion mass spectrometry and 1H-NMR. One of the cytotoxic products isolated was identified as 1-O-octadecyl-2-azelaoylglycerophosphocholine. Methyl esterification of the product confirmed the proposed structure.