Metabolites of non-enzymatic lipid peroxidation of polyunsaturated fatty acids notably omega-3 andomega-6 fatty acids have become important biomarkers of lipid products. Especially the arachidonicacid-derived F2-isoprostanes are the classic in vivo biomarker for oxidative stress in biological systems.In recent years other isoprostanes from eicosapentaenoic, docosahexaenoic, adrenic and -linolenicacids have been evaluated, namely F3-isoprostanes, F4-neuroprostanes, F2-dihomo-isoprostanes and F1-phytoprostanes, respectively. These have been gaining interest as complementary specific biomarkersin human diseases. Refined extraction methods, robust analysis and elucidation of chemical structureshave improved the sensitivity of detection in biological tissues and fluids. Previously the main reliableinstrumentation for measurement was gas chromatography-mass spectrometry (GC-MS), but now theuse of liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunological techniquesis gaining much attention. In this review, the types of prostanoids generated from non-enzymatic lipidperoxidation of some important omega-3 and omega-6 fatty acids and biological samples that have beendetermined by GC-MS and LC-MS/MS are discussed.