In 3 test groups (11 pigs in each group) rations with identical fatty acid patterns (except C 17 acids) at high, medium and low-energy levels of the rations were fed. The fatty acid composition of the lipids of liver, heart and brain was analyzed at the end of the experiments. A correlation was found to exist between energy and fatty acid intake and the fatty acid spectrum of the organ lipids. With identical intake of odd-numbered fatty acids, an energy-rich diet leads to a reduction of odd-numbered fatty acids in the heart and liver lipids. A reduced energy concentration causes an increase of odd-numbered fatty acids in liver and heart. Under energy-rich and energy-reduced feeding, C 15 and C 19 acids can be traced in the hepatic lipids. In liver, heart and brain, an energy-rich diet results in increased contents of eicosapentaene and eicosahexaene acid. Under low-energy diet, a reduction of these fatty acids can be found in the brain.