We investigated the relationship between serum levels of retinol, beta-carotene, alpha-carotene, lycopene, alpha-tocopherol, and gamma-tocopherol as well as intakes of retinol, carotene, and vitamin E and the risks of breast cancer and proliferative benign breast disease (BBD) in a case-control study of postmenopausal women in the Boston, MA (United States) area. Serum nutrient data were available for 377 women with newly diagnosed stage I or II breast cancer and 173 women with proliferative BBD. Controls were 403 women who were evaluated at the same institutions but did not require a breast biopsy or whose biopsy revealed nonproliferative BBD. We observed no significant associations between serum levels of these micronutrients and risk of proliferative BBD or breast cancer. The risk of breast cancer was decreased among women in the highest quintile of intake of vitamin E from food sources only (odds ratio [OR] for the highest quintile = 0.4, 95 percent confidence interval [CI] = 0.2-0.9; P, trend across quintiles = 0.02) but less so for total vitamin E intake including supplements (OR = 0.7, CI = 0.4-1.3; P, trend = 0.07).