Hormone-related supplements (HRS), many of which contain phytoestrogens, are widely used to manage menopausal symptoms, yet their relationship with breast cancer risk has generally not been evaluated. We evaluated whether use of HRS was associated with breast cancer risk, using a population-based case–control study in 3 counties of the Philadelphia metropolitan area consisting of 949 breast cancer cases and 1,524 controls. Use of HRS varied significantly by race, with African American women being more likely than European American women to use any herbal preparation (19.2% vs. 14.7%, p = 0.003) as well as specific preparations including black cohosh (5.4% vs. 2.0%, p = 0.003), ginseng (12.5% vs. 7.9%, p < 0.001) and red clover (4.7% vs. 0.6%, p < 0.001). Use of black cohosh had a significant breast cancer protective effect (adjusted odds ratio 0.39, 95% CI: 0.22–0.70). This association was similar among women who reported use of either black cohosh or Remifemin (an herbal preparation derived from black cohosh; adjusted odds ratio 0.47, 95% CI: 0.27–0.82). The literature reports that black cohosh may be effective in treating menopausal symptoms, and has antiestrogenic, antiproliferative and antioxidant properties. Additional confirmatory studies are required to determine whether black cohosh could be used to prevent breast cancer. © 2006 Wiley-Liss, Inc.