Little information is available concerning whether incorporation of dietary omega-3 fatty acids into plasma lipids changes during healthy aging. Elderly (74 ± 4 years old) and young (24 ± 2 years old) adults were given a fish oil supplement for 3 weeks that provided 680 mg/day of docosahexaenoic acid and 320 mg/day of eicosapentaenoic acid, followed by a 2 week wash-out period. Compliance was monitored by spiking the capsules with carbon-13 glucose, the excretion of which was measured in breath CO₂. In response to the supplement, plasma docosahexaenoic acid rose 42% more in the elderly but eicosapentaenoic responded similarly in both groups. Despite raising docosahexaenoic acid intake by five to tenfold, the supplement did not raise plasma free docosahexaenoic acid (% or mg/dL) in either group. We conclude that healthy aging is accompanied by subtle but significant changes in DHA incorporation into plasma lipids.