This chapter reviews what is known about social relationships between adults. It focuses exclusively on social relationships in which all parties are adults and concentrates on those social relationships in which at least one person is elderly. A life course perspective on social relationships, focusing on how individuals change over time and how their transitions are linked to the people with whom they maintain close relationships, is used. The chapter focuses primarily on adult social relationships between: (1) spouses, (2) parents and their children, (3) siblings, and (4) friends. These bonds are examined both within the context of health and disability, reviewing conceptual frameworks as well as empirical literature. The chapter concentrates on reviewing critical themes, highlighting recently published literature, and identifying key research questions and findings. On the basis of this review of the state of the art, the chapter concludes by making recommendations for future directions that the next generation of knowledge about social relationships between adults should take.