Young rats fed a diet providing 0.3, 3 or 10% of the energy as essential fatty acids (EFA) were given a single intravenous dose of albumin-bound 1-14C-linoleic acid. 1 animal from each group was killed at 1 and 18 h, respectively, after the injection and submitted to whole-body autoradiography. In general, the activities in the tissues were higher in the 0.3% group than in the other groups, whereas the differences between the 3% and the 10% group were small. In all groups the highest activity occurred in the brown fat. High activities were also noted in the liver, the adrenal cortex, the diaphragm, and the gastric and intestinal mucosa. The higher activities in the tissues of the rats fed 0.3 % than in the tissues of those fed 3% or 10% EFA probably reflect a higher incorporation of fatty acids of the linoleic acid series into structural and other lipids in the former group due to the lack of EFA.