Surveys suggest that most patients have a spiritual life and regard their spiritual health and physical health as equally important. Furthermore, people may have greater spiritual needs during illness. We reviewed published studies, meta-analyses, systematic reviews, and subject reviews that examined the association between religious involvement and spirituality and physical health, mental health, health-related quality of life, and other health outcomes. We also reviewed articles that provided suggestions on how clinicians might assess and support the spiritual needs of patients. Most studies have shown that religious involvement and spirituality are associated with better health outcomes, including greater longevity, coping skills, and health-related quality of life (even during terminal illness) and less anxiety, depression, and suicide. Several studies have shown that addressing the spiritual needs of the patient may enhance recovery from illness. Discerning, acknowledging, and supporting the spiritual needs of patients can be done in a straightforward and noncontroversial manner. Furthermore, many sources of spiritual care (e.g., chaplains) are available to clinicians to address the spiritual needs of patients.