Black cohosh (Actaea racemosa, syn. Cimicifuga racemosa) is a popular dietary supplement and currently one of the most promising alternative approaches to hormone replacement therapy for menopausal women. The root and rhizomes, often collected by wild-crafting, are typically used for botanical preparations. There are several species of Actaea that co-occur with black cohosh in the US, and some of these are difficult to differentiate. In addition, Asian Actaea species are being sold as black cohosh. Good botanical and manufacturing practices are hampered by the lack of adequate data about the botanical identification and phytochemistry of the different species in this genus. This study involves the examination of variation in Actaea at the species, population, and seasonal levels. We plan to use DNA and phytochemical fingerprinting methods to distinguish A. racemosa from closely related Actaea species by examining variation in eight North American and four Asian species by DNA barcoding, high-performance liquid chromatography-photodiode array (HPLC-PDA), and liquid chromatography-mass spectrometry (LC-MS) methods that we have developed in our laboratories. We will fingerprint the distinguishing features of 20 populations of black cohosh using phytochemical and DNA (amplified fragment length polymorphisms) methods. We will also examine the seasonal variation of black cohosh constituents. The data will be used to improve the identification of black cohosh. For both basic research on plant systematics and the safe use of black cohosh, it is important to develop reliable DNA and phytochemical fingerprinting methods to identify Actaea species. Our long-range goals are to improve the quality of black cohosh dietary supplements and understand the variation in Actaea species.