Concurrent to a clinical trial of black cohosh for menopausal hot flashes, the long-term stability of the black cohosh, over the duration of the clinical trial, was examined. Analytical results showed that the major constituents, both triterpene glycosides and polyphenols, were stable over the 3-year period of testing. These results indicate that a black cohosh product stored for several years in a controlled environment does not undergo significant changes in its major constituents. These results have implications not only for clinical research in natural products, but for basic science, as well as the dietary supplements industry.