Traditional Chinese medicine has a strong scientific basis, but the science of these important preparations is often rarely discussed. Western approaches often simplify traditional Chinese medicine to drug discovery in Chinese plants, however, the majority of traditional Chinese medications use complex mixtures of plant extracts, rather than single purified drugs. The combination of different extracts is based on yin, yang and chi theories, which are often poorly understood in the West. Yin and yang are known to be the balance of agonists and antagonists, whereas chi derives from signalling processes in the body and regulates bodily functions. Traditional Chinese medical practitioners understand that yin, yang and chi constantly interact in the body to maintain health. Western medical practitioners understand how to use agonists and antagonists and how to modify signalling processes, but generally do not accept the use of complex plant extracts to perform these functions. Aimed at medical scientists, and including detailed explanations of the theories behind the science, this text may help researchers to understand Chinese medical practitioners and to communicate more effectively with them. It will also lead to greater acceptance of traditional medications in the West. Presenting a clear rationale for the use of traditional Chinese medications in Western medical facilities, it enables scientists to find new directions in experimental design and encourage examination of these useful, but often poorly understood, preparations in clinical trials.