Marriage – the most important adult relationship in most people’s lives – has been theorized to affect biological processes, physical health, and mortality. This article highlights key findings in marriage and health research, focusing on the interpersonal processes through which marriage has been proposed to affect health. A model of marriage and health is presented that incorporates both main and stress-moderating effects of negative marital experiences –marital strain– and positive marital experiences –marital strength. Although many more studies have investigated marital strain than marital strength, current evidence suggests that both have potent effects on biology and health. The article concludes with a discussion of implications of this research for social and personality psychology, focusing on insights that may be gained from basic relationship science. Examples of three areas of relationship research – intimacy processes, commitment processes, and dyadic analysis – and their potential relevance for marriage and health research are presented.