Reiki is a noninvasive, nondiagnostic, and nondirective hands-on healing therapy which is believed to promote healing and a state of well-being in all living things. In recent years, its popularity has increased and as a bio eld or energy therapy it is being used as a complementary modality with the conventional medical care in a variety of settings. Reiki is a Japanese term meaning universal life force which is believed to ow from the hands of a practitioner to a willing recipient’s body facilitating physical, emotional, or spiritual healing depending on the needs of the recipient. is article provides a comprehensive review of the information available about Reiki in the areas of its history and development, nature of training and treatment protocol, practice ethics, empirical research and challenges for the researchers, guidelines for future research, and current applications. ere is a vast amount of anecdotal, published, unpublished, and Internet information available on the subject of Reiki and its use as a healing modality with discrepancies among many sources. is article attempts to sort out and present only that information which is accepted by majority of the Reiki practitioners and as such is an informative reading for all health practitioners.