In Chapter 6, I illustrate the current strengths and limitations of applying relationship theories to health and illness transitions. I outline theoretical assumptions for exemplary relationship theories to show strengths and limitations of understanding health and illness trajectories through relationship theories. For example, I show how exemplary relationship theories account for illness as a relational transition, point of turbulence, or relational stressor. I illustrate examples of relationship theories that explain how interactions are constrained or enhanced by the contexts in which they take place. In the application of key relationship theories in the context of health and illness, I illustrate how relationship theories shed light on shifted interdependence processes during illness diagnosis, management, and ongoing sense-making.