This chapter provides a definition and description of the concept of school refusal behavior in children and adolescents. The chapter focuses on definitions of key terms, epidemiology, common behaviors and symptoms associated with problematic absenteeism, and short- and long-term outcomes of problematic absenteeism. However, a main focus is on how these characteristics pertain to, and illustrate, the real-life cases seen by the reader. Chapter 1 also include an overview of the book’s approach. The chapter discusses the purpose of this book and characteristics of youths with school refusal behavior. The chapter also presents a model for understanding school refusal behavior and for guiding assessment and intervention.