The purpose of this handbook is to provide the researcher, clinician, teacher and student in all mental health fields with comprehensive coverage of this important area of child psychopathology. The Disruptive Behaviour Disorders (as labelled in DSM IV) are Attention Deficit/Hyperactivity Disorder (three subtypes), Conduct Disorder (two subtypes), and Oppositional Defiant Disorder. Taken together, these disorders account for at least three fourths of the combined prevalence of all psychopathological disorders of childhood and adolescence. An understanding of the biological and psychosocial aetiologies of these disorders, the settings that engender and maintain them, their natural history, and what may be the most effective intervention and prevention strategies for them should be of importance to all professionals who must deal with these troubled youths.