Intrauterine growth retardation (IUGR) was obtained by ligation of one uterine artery on day 17 of pregnancy. Neurons isolated from IUGR rats presented a decrease of monounsaturated fatty acids and an increase of omega-3 serie fatty acids, concomitant to a decrease of omega-6 serie fatty acids. Oligodendrocyte content in monounsaturated fatty acids was also reduced; important modifications occurred in their polyunsaturated fatty acid distribution. Myelin was close to normal in adults, slightly altered in young. Synaptosomes presented slight disturbances in polyunsaturated fatty acid distribution. Thus, the fatty acid composition was an index of maturation stage and nutritional status of developing brain membranes.