A randomized clinical trial evaluated the therapeutic efficacy of group cognitive-behavioral therapy (GCBT) versus a wait-list control (WLC) condition to treat anxiety disorders in children. Results indicated that GCBT, with concurrent parent sessions, was highly efficacious in producing and maintaining treatment gains. Children in GCBT showed substantial improvement on all the main outcome measures, and these gains were maintained at 3-, 6-, and 12-month follow-ups. Children in the WLC condition did not show improvements from the pre- to the postwait assessment point. These findings are discussed in terms of the need to continue to advance the development of practical, as well as conceptual, knowledge of efficacious treatment for anxiety disorders in children.