The purpose was to evaluate faith-based studies within the medical literature to determine whether there are ways to help physicians understand how religion affects patients’ lives and diseases. We reviewed articles that assessed the influence of religious practices on medicine as a primary or secondary variable in clinical practice. This review evaluated 49 articles and found that religious faith is important to many patients, particularly those with serious disease, and patients depend on it as a positive coping mechanism. The findings of this review can suggest that patients frequently practice religion and interact with God about their disease state. This spiritual interaction may benefit the patient by providing comfort, increasing knowledge about their disease, greater treatment adherence, and quality of life. The results of prayer on specific disease states appear inconsistent with cardiovascular disease but stronger in other disease states.