Background: Antioxidant defenses are one possible mechanism for decreasing oxidative damage and its potentially negative effects on age-related bone mass. Objective: This study cross-sectionally examined whether higher dietary intakes, total intakes, and serum concentrations of antioxidants may be associated with higher bone mineral density (BMD). Design: Total hip (and subregions), spine, and total-body BMDs were measured in 11 068 women aged 50-79 y enrolled in the Women's Health Initiative Observational Study and Clinical Trial at 3 clinics. Antioxidant intakes from diet (vitamin A, retinol, β-carotene, vitamin C, vitamin E, and selenium) were estimated by using a self-reported food-frequency questionnaire. Antioxidants from supplements were estimated with an interviewer-administered questionnaire. A random subset (n = 379) had serum concentrations of retinol, carotenoids, and tocopherols measured. Results: After adjustment for important BMD-related covariates, increasing intakes of antioxidants were not independently associated with BMD. A significant interaction effect was observed between intake of total vitamin C (lower three-fourths compared with highest one-fourth) and use of hormone therapy (HT) (P < 0.01). The beneficial effect of current HT use on femoral neck BMD appeared to be greater in women with higher concentrations of total vitamin C. This interaction was also significant for total-body (P < 0.045), spine (P = 0.03), and total-hip BMDs (P = 0.029). Conclusions: Our results do not support independent associations between dietary intake, total intake, or serum concentrations of antioxidants and BMD in women participating in the Women's Health Initiative. The extent to which HT use may interact with vitamin C intake and BMD warrants further exploration. © 2005 American Society for Clinical Nutrition.