This chapter reviews prior dyadic research that has examined the processes through which romantic partners and relationships affect physical health outcomes. It carefully delineates how individuals in a romantic relationship affect each other's health behavior, which in turn may affect their health outcomes. The chapter examines the personal, relational, and situational factors that might affect the way in which relationship partners affect each other's health-relevant behavior. It discusses several different ways in which partner beliefs can affect the actor's psychological and behavioral processes linked to the actor's long-term health outcomes, which is one important component contributing to general well-being. The chapter identifies the health behaviors that she/he was attempting to influence the actor to change. Behavioral processes have received less attention than psychological or biological processes in research on relationships and health outcomes. Several studies have tested the impact that partner influence strategies have on the actor's behavior.