The aim of this study was to evaluate the serum coenzyme Q10 concentrations of healthy elderly women before and after supplementation with coenzyme Q10 combined with multivitamins, selenium, and magnesium. In a randomized double-blind design, 220 free-living women aged 60 years and older were included. Median serum coenzyme Q10 concentration at baseline was 0.99 mumol/L (5-95 percentiles: 0.54-1.68) and cholesterol adjusted concentration was 0.16 (5-95 percentiles: 0.09-0.26) mmol/mol cholesterol. No significant correlations were found between Q10 levels and body mass index (BMI) or age. Q10 concentrations were not significantly different between smoking and nonsmoking women, nor between women with statin therapy and without. Furthermore no differences were seen between hyperlipidemic and normolipidemic subjects. Cholesterol-adjusted Q10 levels were positively correlated to lipid-adjusted serum tocopherol levels and negatively associated to serum beta-carotene. No significant correlation existed between adjusted Q10 levels and plasma selenium. Results of the food diaries showed a significant but weak correlation to meat and meat products and to alcohol intake. At baseline, Q10 levels did not differ between supplemented and control group. After six months, adjusted serum concentrations of the supplemented and the control group were significantly increased by 106% and 31%, respectively. In the supplemented group the change was inversely associated with the baseline concentration. A six-month supplementation with coenzyme Q10, vitamins, and selenium raises the blood concentration of coenzyme Q10 even in relatively well-nourished elderly women.