The plasma lipid fatty acid (FA) profile was measured in 83 healthy subjects (35 men, 48 women; ages 18-82 y). The association of 19 variables (including serum antioxidant micronutrients) with saturated (SFA), monounsaturated (MUFA), essential (EFA), and polyunsaturated fatty acid (PUFA) status was assessed by stepwise multiple-linear regression. Serum selenium was directly associated with percent EFA and n-6 PUFA (r = 0.38, P = 0.0004 for both) and inversely related to percent SFA in phospholipids (r = -0.38, P = 0.0004). Serum selenium was the only predictor of the unsaturation index of this fraction (r = 0.45, P = 0.0000). Although associations of plasma FA pattern with age, serum cholesterol, bilirubin, vitamin E, and zinc were also disclosed, only for selenium did the antioxidant effect seem to explain this relationship. These results suggest that antioxidant micronutrients should be measured when PUFA metabolism is studied. The relationship between plasma FA and antioxidant micronutrients in disease states needs further research.