Reiki is a vibrational, or subtle energy, therapy most commonly facilitated by light touch, which is believed to balance the biofield and strengthen the body's ability to heal itself. Although systematic study of efficacy is scant thus far, Reiki is increasingly used as an adjunct to conventional medical care, both in and out of hospital settings. This article will describe the practice and review the history and theory of Reiki, giving readers a context for the growing popularity of this healing modality. Programs that incorporate Reiki into the clinical setting will be discussed, as well as important considerations in setting up such a program. Finally, the research literature to date on Reiki will be reviewed and evaluated, and directions for future Reiki research will be suggested.