This report was commissioned by the Women's Sports Foundation to better understand the impact of sports participation on teen health, well-being and academic achievement. They sought to understand how each sport impacts teen well-being, and whether the number of sports in which a teen participates influences their health. They also sought to better understand whether sports opportunities overall, as well as individual sports, are accessible to all teens across genders, race and ethnicities, levels of family income and regions. Finally, they wanted to identify the unique benefits and opportunities for improvement that exist within each sport to maximize the health benefits for teens. The research is based on an analysis of the Monitoring the Future (MTF) nationwide surveys, a federally funded longitudinal study of American secondary students. The authors evaluated 20 sports most commonly accessible to American teen girls and boys to identify which sports are doing well in promoting health and preventing risk, and which have room for improvement. This included the 13 most popular sports in the U.S. (baseball/softball, basketball, cheerleading, cross-country, football, golf, lacrosse, soccer, swimming/ diving, tennis, track and field, volleyball, and wrestling) and seven emerging youth sports (crew, equestrian, field hockey, gymnastics, ice hockey, water polo, and weight lifting). All data analyses controlled for key sociodemographic variables like sex, race, and socioeconomic status. Key findings of the report include: (1) sports are transformative in the lives of teens; (2) the numbers of sports teens participate in matters; (3) each sport provides a unique impact on health; (4) room for improvement exists in some areas, especially in certain sports; (5) diversity and disparities in sport depend on geographic region and type of sport; and (6) the time for sport-by-sport has come. [The policy recommendations were authored by Bruce Y. Lee. Lead funding was provided by the Laureus Sport for Good Foundation USA. Additional funding was provided by Kerry Burrows and Colleen May. For the executive summary, see ED588345.]