"Her Life Depends On It III" (HLDOI) is the Women's Sports Foundation's comprehensive report that reviews existing and emerging research on the links between participation in sport and physical activity and the health and well-being of American girls and women. As with the previous editions in 2004 and 2009, this study also confirms that physical activity and sport provides the critical foundation, in no small part, that allows girls and women to lead healthy, strong, and fulfilled lives. This executive summary recognizes that ten years since its first publication, the updated "Her Life Depends On It" provides an even more comprehensive review of the ever-expanding body of research that demonstrates how important it is for girls and women to participate in sport and physical activity. The full report's contents reflect the review of 1,500 studies, nearly 400 covered since the previous edition. While the report's focus continues to be on U.S. girls and women, selected research findings that offer perspective regarding girls and women worldwide is also referenced in order to provide some perspective and context. In keeping with previous editions of the report (Sabo et al, 2004; Staurowsky et al., 2009), this updated review of existing research and health information is co-authored by a team of experts from several related disciplines, including epidemiology, exercise physiology, kinesiology, psychology, sociology, and sport management. "Her Life Depends On It III" documents the important role physical activity can play in helping to prevent the daunting array of health risks for girls and women, such as cancer, coronary heart disease, osteoporosis, Alzheimer's Disease and related dementias, eating disorders, illicit drug use, obesity, risky sexual behavior and teen pregnancy, and tobacco-related diseases. With the clarity of a ringing bell, research affirms, even more definitively than five years ago, that engagement in moderate and consistent levels of physical activity and sport for girls and women is essential to good health and well-being. [For the full report, see ED570479.]