National Cancer Institute (NCI) funded cooperative oncology group trials have improved overall survival for children with cancer from 10% to 85% over the past five decades, and have set standards of care for adults with malignancies. However, according to the Institute of Medicine: "the clinical trial system is approaching a state of crisis". If [it] does not improve its efficiency and effectiveness, the introduction of new treatments for cancer will be delayed and patient lives will be lost unnecessarily. This application proposes to improve toxicity monitoring, estimate treatment associated resource utilization and costs, and serve as a platform for answering important clinical epidemiology questions by merging data from the Children's Oncology Group (COG) and the Pediatric Health Information Systems (PHIS) administrative data base for patients treated for de novo acute myeloid leukemia (AML) on recent Phase III clinical trials. Four hypotheses underpin this application: (1) We hypothesize that greater than 95% of patients enrolled on recent and current COG AML trials can be identified in PHIS; (2) COG-PHIS merged data will more accurately report adverse events than unmerged data; (3) COG-PHIS merged data can prospectively monitor a Phase III trial for adverse events; (4) COG-PHIS merged data will describe standardized costs of treatment by regimen arm and enable analyses of cost variation. This application has significance both as a methodological advancement and in the use of this methodology to improve toxicity monitoring and outcome analysis in cooperative group oncology trials. Furthermore, this application is highly innovative as the first merging of cooperative grou clinical trial data with administrative data. Finally, the approach taken in this application shoul be applicable not only to other pediatric malignancies, but also to adult cancers generally. Thus, the application is likely to have a high impact on the care of both children and adults with cancer.