A convenient method for the preparation of hydroperoxy and hydroxy derivatives of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) is described. PC and PE obtained from rat liver were oxidized with singlet oxygen by using methylene blue as the photosensitizer, and their hydroperoxides were isolated with the aid of reverse phase liquid chromatography. The hydroxy derivatives were obtained by reducing the hydroperoxides with sodium borohydride. The results of gas chromatography mass spectrometry revealed that hydroxy fatty acid components of the hydroxy derivatives were derived from isomeric hydroperoxides of oleic acid, linoleic acid, arachidonic acid and docosahexanoic acid. Normal phase high performance liquid chromatography did not separate the hydroperoxy and hydroxy derivatives from the respective unoxidized phospholipids, although unoxidized PC and PE were separated from each other. However, the hydroperoxy and hydroxy derivatives could be distinguished from unoxidized phospholipid species on reversed phase thin layer chromatography.