Marriage is the central relationship for most adults and has beneficial effects for health. At the same time, troubled marriages have negative health consequences. This review outlines the physiological pathways through which marital relationships influence health based on a stress/social support model. In addition, we review recent findings suggesting that unhappy marriages are associated with morbidity and mortality. We then turn to studies of marital interaction that include assessment of physiological pathways through which marital functioning influences health: the cardiovascular, endocrine, and immune systems. Across these studies, negative and hostile behaviors during marital conflict discussions are related to elevations in cardiovascular activity, alterations in hormones related to stress, and dysregulation of immune function. Using recent conceptualizations of the physiological impact of chronic stress, we illustrate how physiological changes associated with marital functioning in these studies have long-term implications for health outcomes. Finally, we discuss future implications of current research for understanding the relationships among marital functioning, physiology, and health.