Although mild worry is normative, children with Generalized Anxiety Disorder (GAD) experience worry that is intense, difficult to control, and impairing. Common worries of children with GAD may relate to perfectionism, performance, social situations, family, community/world events, or health. GAD co-occurs not only with other internalizing disorders (e.g., depression) but also with externalizing problems. A careful, multi-informant assessment is likely to help differentiate GAD from other disorders and also facilitate treatment planning. Research has found support for a number of variables in the etiology and maintenance of GAD including genetic, biological, familial, and environmental influences, cognitive processes, and personality traits and temperamental factors. The course of GAD is characterized by a chronic and episodic wax and wane of symptoms over a fairly long period of time though at least a few treatment approaches are promising. Numerous studies provide support for the use of cognitive behavior therapy (CBT) in treating GAD in youth, and preliminary data suggests that selective serotonin reuptake inhibitors (SSRIs) can also be helpful. The most apparent limitation of the extant literature that is reviewed is the lack of focus on youth with GAD in particular. Future research needs to compare youth with GAD to youth with other types of anxiety disorders.