Yin-yang theory provides a basis for decision-making in the practice of Traditional Chinese Medicine (TCM). Yin-yang thinking is substantially different from the classical approaches used in Western biomedicine, and in TCM, treatments are designed to balance these two forces. According to yin-yang theory, an individual's qualities may be simultaneously opposite and yet complementary. Yin always possesses characteristics of yang and vice-versa. Even though they are opposites, yin and yang are interdependent, can transform into each other, and can consume each other. In TCM, health and illness are viewed as relative states along a continuum, and a state of good health is determined by the dynamic balance between the two. Since no two people are exactly alike as far as their yin and yang characteristics, treatments are individualized in an effort to maximize the end results. Acupuncture is based on the premise that there are well-defined patterns of energy flow throughout the body. This energy is called Qi (pronounced chee). In the Chinese language, the symbol representing Qi indicates something that is simultaneously material and immaterial. Therefore, some TCM practitioners define Qi as matter + energy, expressing the same continuum of matter and energy explained by modern particle physics. Acupuncture treatments are designed, in part, to balance and regulate the flow of Qi. Balancing and regulating Qi can also balance and regulate the yin-yang forces of each organ system throughout the body.

Since the late 1950's, thousands of studies have been published about TCM. Although the specific mechanisms are not completely understood, basic scientific research has revealed that bioelectromagnetic and neurohumoral changes help explain the effects of acupuncture on various types of health problems. The stimulation of acupuncture points is believed to cause biochemical changes that affect the body's natural healing abilities. These changes include enhanced conduction of bioelectromagnetic signals, activation of opioid peptides, and activation of the autonomic and central nervous systems causing the release of various neurotransmitters and neurohormones.