Recent experimental studies in both animal and humans have begun to demonstrate some measurable physiologic effects that are associated with acupuncture, suggesting the possibility of a neurophysiologic explanation. In addition, brain research continues to uncover a complex set of endogenous neurologic control systems, such that it has become clear that the brain plays a major role in the modulation of pain perception and control. If acupuncture can be demonstrated to have a consistent effect on specific areas of the brain, it will become possible to explore the potential efficacy of acupuncture based on measurable neurophysiologic responses.