Treatment participation was examined among youth enrolled in an evaluation of cognitive behavioral therapy (CBT) for trauma following the 9/11 World Trade Center disaster. Staff at nine agencies serving a predominantly low-income, ethnically diverse population were trained to deliver CBT and structured engagement strategies. A total of 445 youth ages 5 to 19 were eligible for CBT, and 417 (94%) received at least one treatment session. Pretreatment and treatment show rates and overall dose were examined. Treatment participation rates were higher than those typically reported in community studies of children's mental health services. Regression analyses indicated variability across sites in treatment show rates with the highest rates at sites where services were delivered in schools. However, sites, demographic factors, and trauma symptoms accounted for a small amount of variance in treatment participation overall. The study suggests that structured engagement strategies, linked to evidence-based treatments, may improve treatment participation for youth. (Contains 4 tables and 1 figure.)