The primary purpose of this chapter is to finish presentation of the cognitive–behavioral therapy (CBT) model with a discussion of the etiology and maintenance of social anxiety. Clients vary on how much they want to know about some of the details. However, nearly everyone asks about etiology at some point in treatment. Possible causes of social anxiety include a genetic component, family environment, and important experiences. However, most psychologists agree that social anxiety disorder, like most other psychological disorders, is not caused by just one thing and results from a combination of factors. This chapter includes the beginning of monitoring progress using the SASCI (Social Anxiety Session Change Index). From this point in therapy forward, at the beginning of each session, clients complete the SASCI.