Childhood obesity is highly prevalent in the United States (U.S.) and has become a global epidemic. The recent national survey, the 2007–2008 National Health and Nutrition Examination Survey (NHANES) data showed that 17 percent of U.S. children and adolescents (ages 2–19) years were obese, and over 30 percent were overweight or obese. Childhood obesity leads to obesity in adulthood and many other serious health conditions, such as cardiovascular, metabolic, and psychosocial illnesses. To assess the effectiveness of existing childhood obesity prevention efforts, the Johns Hopkins University Evidence-based Practice Center completed a systematic review on childhood obesity prevention studies conducted in high-income countries. This report, funded by the Agency for Healthcare Research and Quality (AHRQ), systematically reviewed seven Key Questions. The draft Comparative Effectiveness Review evaluated 96 intervention studies reported in 113 articles with the following main conclusions: The majority of studies in high income countries are conducted in schools. School-based intervention can prevent overweight and obesity, especially those with a home intervention that targets both diet and physical activity. Though the strength of evidence is moderate to high for school-based interventions, the limited number of studies and insufficient or low strength of evidence to support interventions in other settings made it difficult to conclude that interventions in other settings could effectively prevent childhood obesity. Based on the evidence gaps in these settings, we identified the following as Future Research Needs: Future research is needed on interventions delivered in settings other than schools or home. Thus, future research is needed for all of the Key Questions except for Key Questions 1 and 2, and especially needed are studies of environmental and policy changes. While there have been other reviews on the effectiveness of interventions on food and nutrition policies at school on changes in children’s diet and school food environments, there are still gaps in the literature on some aspects, such as the impact of regulations on food availability and its impact on obesity prevention. Only a few studies that we reviewed used social marketing to deliver messages on nutrition, physical activity and health. This approach might be integrated with other intervention components to create an atmosphere favorable to healthy and active lifestyles and related behavioral changes. Additionally, further testing of the value of consumer health informatics products for obesity prevention is needed. In addition, there is a lack of evidence on the impact of regional or national policies on childhood obesity prevention, including agriculture policy and regulations on food retailing and distributions. Furthermore, further research might be conducted with stratified analyses on subgroups, such as by gender, age, race/ethnicity, or socioeconomic status. This will help us learn how different groups may respond differently to the same intervention, and help tailor future interventions to maximize their benefits. There were methodological limitations of the reviewed studies which suggest that future research might improve upon the methods. Few of the studies we reviewed reported process evaluation, which would provide useful insight regarding why some studies might detect desirable effect of the intervention. More vigorous analytic approaches are desirable in future studies, to better analyze the repeated measures collected during follow-up, to control for confounders, and to test effect modification. The studies we reviewed typically had limited followup and we could not know the sustainability of these interventions. Future studies need to design innovative approaches that have a high likelihood of sustainability; for example, studies using a community-based participatory approach. This may be designed to take advantage of other existing public health, government or other organization supported programs or try to gain more support and engagement from related key stakeholders. The objective of this report is to prioritize the needs for research addressing gaps in the existing literature on the effectiveness of childhood obesity prevention programs by engaging expert stakeholders using a modified Delphi method.