BACKGROUND: Several recent reviews have reached guardedly positive conclusions about the effectivenessof biofield therapies in healthcare.(1,2) These studies mainly involved randomized controlled trials to determine changes in condition-related outcome measures, but few addressed the biological basis of these effects. STUDY OBJECTIVE AND RATIONALE: We performed a systematic review of studies designed to examine whether biofield therapists undergo physiological changes as they enter the healing state. If reproducible changes can be identified, they may serve as markers to reveal events that correlate with the healing process. METHODS: Databases were searched for controlled or non-controlled studies of biofield therapies in which physiological measurements were made on practitioners in a healing state, with or without a healee present. Design and reporting criteria, developed in part to reflect the pilot nature of the included studies, were applied using a yes (1.0), partial (0.5), or no (0) scoring system. RESULTS: Of 67 identified studies, the inclusion criteria were met by 22, 10 of which involved human healees. Overall, the studies were of moderate to poor quality and many omitted information about the training and experience of the healer. The most frequently measured biomarkers were electroencephalography (EEG) and heart rate variability (HRV). EEG changes were inconsistent and not specific to biofield therapies. HRV results suggest an aroused physiology for Reconnective Healing, Bruyere healing, and Hawaiian healing but no changes were detected for Reiki or Therapeutic Touch. CONCLUSIONS: Despite a decades-long research interest in identifying healing-related biomarkers in biofield healers, little robust evidence of unique physiological changes has emerged to define the healers? state.