This chapter discusses the process of clinical case formulation, which emerges from our assessment and guides our thinking about a treatment plan that will be helpful to our client. A clinical case formulation is a necessary step in an effective treatment. The case formulation also provides an orientation and guide during treatment as circumstances and crises change. A cognitive-behavioral case formulation will emphasize cognitive schemas as well as biological and social factors that contribute to and maintain a particular emotional or behavioral state. A psychodynamic case formulation will emphasize particular affective states, defenses, and representations of self and others that are related to the development of the client's psychological symptoms. A case formulation for couple or family treatment generally has a primary focus on the relationship dynamics and structure, but needs to include a description of how each individual contributes to the difficulties in the couple or family system.