People have used herbal medicines throughout history and they are currently the most commonly used medicines world-wide. In spite of this, the effectiveness and safety of herbal medicines is less well demonstrated and understood than that of conventional medicines. Numerous problems have been found in the quality of commercial herbal medicine products. These problems include a lack of consistency of active ingredients, contamination with other herbs and toxins, inaccurate content, and adulteration with conventional medicines. In contrast to other industrialized countries, there is little regulation of herbal medicines in the U.S. This leaves consumers who wish to use herbal medicines with few guarantees about which ones are safe and effective. This review provides a general discussion of herbal medicines, especially those that may act on the breast or affect breast cancer risk.