This text weaves evidence from wide-ranging fields into a coherent theory of challenging behaviour. The result should be a better understanding of the nature of challenging behaviour in people with developmental disabilities, but also a clearer delineation of the basic principles that guide assessment and intervention. The authors explore the various individual traits, social context and environmental factors that influence the development and persistence of aggression, self-injury, extreme tantrums, and other common forms of challenging behaviour. Ethical issues that arise in supporting individuals with challenging behaviour in typical home, school and community settings are exposed, as are the difficulties of designing treatments without knowledge of the causes of the behaviour. Reliance on the more typical, technique-driven approach is discarded in favour of an evidence-based approach that focuses on the basic principles that underlie effective interventions. With its focus on the basic principles that underlie effective clinical practice, this book should be of use to graduate students, beginning researchers and clinicians in psychology, special education, speech and language therapists, occupational therapy, social work and related disciplines.