Although much has been written about the importance of assessment and intervention related to the patient's spiritual or religious needs, there is little understanding of the influence that the health care provider's religiosity has on the care they deliver to patients. This concept analysis of religiosity uses Rodger's evolutionary methodology to begin to develop an understanding about the definition of religiosity in health care in order to provide a basis for continued exploration of the articulation between patient and provider religiosity, particularly as it relates to nursing. This review found that there are many instruments for assessing and measuring religiosity and that they are used in varying ways. There is considerable consistency related to a definition of religiosity that includes religious affiliation, religious activity, and religious belief.