The importance of antioxidants in reducing risks of chronic diseases has been well established; however, antioxidant intakes by a free-living population have not yet been estimated adequately. In this study, we aimed to estimate total antioxidant intakes from diets and supplement sources in the U.S. population. The USDA Flavonoid Database, food consumption data, and dietary supplement use data of 8809 U.S. adults aged >/=19 y in NHANES 1999-2000 and 2001-2002 were used in this study. Daily total antioxidant intake was 208 mg vitamin C (46 and 54% from diets and supplements, respectively), 20 mg alpha-tocopherol (36 and 64), 223 mug retinol activity equivalents carotenes (86 and 14), 122 mug selenium (89 and 11), and 210 mg flavonoids (98 and 2). Antioxidant intakes differed among sociodemographic subgroups and lifestyle behaviors. Energy-adjusted dietary antioxidant intakes were higher in women, older adults, Caucasians, nonconsumers of alcohol (only for vitamin C and carotenes), nonsmokers (only for vitamin C, vitamin E, and carotenes), and in those with a higher income and exercise level (except for flavonoids) than in their counterparts (P < 0.05). Consumption of fruits, vegetables, and whole grains may be a good strategy to increase antioxidant intake. The possible association between antioxidant intake and the prevalence of chronic diseases should be investigated further.