Abstract.Growing interest in nutritional intervention with n‐3 polyunsaturated fatty acids demands reliable analyses of these fatty acids and their corresponding eicosanoidsin vivoorex vivo. n‐3 polyunsaturated fatty acids are preferably assayed by capillary gas‐liquid chromatography after extraction of the lipid classes, their separation by chromatographic methods and conversion of the fatty acids to methylesters. n‐3 eicosanoids have to be separated from their arachidonic acid analogues by HPLC or by gas‐liquid chromatography and are then quantified by UV‐spectroscopy or mass‐spectrometry. Structure elucidation has to be performed by chemical reactions and by mass spectrometry. Antibodies for radioimmunoassays against n‐3 eicosanoids are no