In this third of a four-article series on religion and medicine, I describe a theoretical model to illustrate the complex pathways by which religion may influence physical health. Genetic factors, childhood training, psychological and social influences, health behaviors, and healthcare practices are discussed as part of this model. Considerable space is given to recent advances in psychoneuroimmunology and to stress-induced cardiovascular changes that demonstrate physiological pathways by which cognitive, emotional, and behavioral processes may influence susceptibility to disease and disease course. I also discuss research illustrating the important role that social support plays in moderating the physiological effects of stress and improving health outcomes. If religious beliefs and practices improve coping, reduce stress, prevent or facilitate the resolution of depression, improve social support, promote healthy behaviors, and prevent alcohol and drug abuse, then a plausible mechanism exists by which physical health may be affected.