The effects of antioxidants on the fatty acid composition of cultured aortic smooth muscle cells obtained from normal, hypercholesterolemic and aged rabbits were studied in vitro. α-Tocopherol and coenzyme Q(10) were used as antioxidants.Cell lipid extracts were separated into cholesterol ester (CE), triglyceride (TG) and phospholipid (PL) fractions by thin layer chromatography. The fractions were analyzed by gas-liquid chromatography for fatty acid composition. Upon addition of α-tocopherol, the proportion of oleate (18:1) increased and that of linoleate (18:2) decreased in the CE and TG fractions, but that of stearate (18:0) increased and those of linoleate and arachidonate (20:4) decreased in the PL fraction.These effects of α-tocopherol were most significant in HL-SMC, and almost no change in Aged-SMC was observed.Addition of coenzyme Q(10) resulted small changes in the fatty acid composition of the cultured cells and culture media.