We propose that essential fatty acids are very important for hibernation and reproduction in mammals. The proposed research will focus on fatty acid composition, uptake and utilization in the white adipose tissue and liver of marmots (Marmota flaviventris) by season and will directly assess if one particular essential fatty acid, linoleic acid (18:2, n-6), is spared Beta oxidation to a significant degree within these tissues during the hibernation period, October to March. It is well known that linoleic acid is very important not only as an energy supply, but also as the precursor for arachidonic acid (20:4), and perhaps is important for changes in reproductive condition and thermoregulatory capabilities during, and at the end of hibernation. As marmots are mammals, the results from these experiments may be directly applicable to the human metabolic disorders. Several human pathological conditions are associated with essential fatty acid deficiency. Consequently, conclusions drawn from these experiments will enhance our knowledge about the role of essential fatty acids in physiological processes.