Adipocere formation is well known as a later postmortem change. We collected adipocere from five male victims which had been submerged under the sea or fresh water for 1 mon to 4 yr. Fresh subcutaneous fat of a male victim who died from a cerebral contusion was used as the control. The samples were homogenized, and the lipids were extracted with chloroform and methanol followed by injection into a gas chromatograph and a gas chromatograph-mass spectrometer. We detected hydroxy fatty acids (10-hydroxyoctadecanoic acid and 10-hydroxyhexadecanoic acid) as well as 10-ketooctadecanoic acid in adipocere, but not in the control. In addition, we found for the first time a cholesterol-related peak with a molecular ion of 388 in adipocere and identified it as epicoprostanol, suggesting not only oxidation but also reduction had occurred during the formation of adipocere. In addition, we showed the time-course of epicoprostanol accumulation. The relationship between the time of adipocere formation and the characteristic lipid composition is discussed.