The current article reviews the research conducted in the United States on the clinical practice of chaplains with patients and family members, referrals to chaplains, patient satisfaction with chaplaincy services, and the limited literature on the efficacy of chaplain interventions. It also discusses the methodological limitations of studies conducted on these topics and makes suggestions for improving future chaplaincy research. The authors conclude that past studies have not adequately defined chaplain interventions, nor sufficiently documented the clinical practice of chaplains, and that more and better designed studies are needed to test the efficacy of chaplaincyinterventions. The authors recommend that chaplains generate research-based definitions of spirituality, spiritual care, and chaplaincypractice; and that more research be conducted to describe the unique contributions of chaplains to spiritual care, identify best chaplaincypractices to optimize patient and family health outcomes, and test the efficacy of chaplaincy care.