Oppositional defiant disorder is defined by the Diagnostic and Statistical Manual of Mental Disorders, 4th ed., as a recurrent pattern of developmentally inappropriate, negativistic, defiant, and disobedient behavior toward authority figures. This behavior often appears in the preschool years, but initially it can be difficult to distinguish from developmentally appropriate, albeit troublesome, behavior. Children who develop a stable pattern of oppositional behavior during their preschool years are likely to go on to have oppositional defiant disorder during their elementary school years. Children with oppositional defiant disorder have substantially strained relationships with their parents, teachers, and peers, and have high rates of coexisting conditions such as attention-deficit/hyperactivity disorder and mood disorders. Children with oppositional defiant disorder are at greater risk of developing conduct disorder and antisocial personality disorder during adulthood. Psychological intervention with both parents and child can substantially improve short- and long-term outcomes. Research supports the effectiveness of parent training and collaborative problem solving. Collaborative problem solving is a psychological intervention that aims to develop a child's skills in tolerating frustration, being flexible, and avoiding emotional overreaction. When oppositional defiant disorder coexists with attention-deficit/hyperactivity disorder, stimulant therapy can reduce the symptoms of both disorders.