The long-chain polyunsaturated fatty acids (LC PUFAs) docosahexaenoic acid (DHA, 22:6n3) and eicosapentaenoic acid (EPA, 20:5n3) are important for health and development of organisms, but the precise biological function of these molecules is not known. It has been suggested that they may play a part in aging, as they are highly susceptible to oxidation. A genetic mutant of Caenorhabditis elegans (fat-3), which lacks a functional delta-6 desaturase, and thus LC PUFAs including EPA, allows dietary manipulation of long-chain n3 fatty acids in this nematode. The life span of C. elegans strains N2 (wild-type) and BX30 [fat-3(wa22)] with and without supplemental EPA and DHA was analyzed. In addition, quantitative analysis was performed on total lipids, phospholipids, and triglycerides, as it is important to understand where fatty acids are being partitioned among the various lipid classes. The results show a beneficial effect of these molecules on the life span of C. elegans and will aid in the elucidation of the underlying causes of PUFA deficiency in the simple animal C. elegans as well as in humans.