This randomized clinical trial compared cognitive behavioral therapy (CBT) with minimal parent involvement to CBT with active parent involvement in a sample of 119 youths (7-16 years old; 33.6% Caucasian, 61.3% Latino) with anxiety disorders. The dynamics of change between youth anxiety and parent variables (positive-negative behaviors toward the child, conflict in the parent-youth relationship, and parental anxiety) in both treatment conditions over pretreatment, posttreatment, and 12-month follow-up were also examined. Results indicated that youth anxiety was significantly reduced with both treatments and that the dynamics of change may not solely flow from parent to youth but also from youth to parent. Findings highlight the need for research on directionality and mechanisms of change to move from evidence-based treatments toward evidence-based explanations of treatment outcome. (Contains 3 tables and 2 figures.)