Arguably, the most important school-based intervention to increase physical activity was Title IX of the Education Amendments of 1972, which led to a 600% increase in girls' sports participation between 1972 and 1978. We studied the effect of this increase in sports participation and athletic opportunities while young on the physical activity and weight of adult women some 20-25 years later. Our results indicate that adult women who were affected by Title IX and had greater opportunity to participate in athletics while young had lower body mass index (BMI) and lower rates of obesity and reported being more physically active than women who were not afforded these opportunities. However, effect sizes were quite modest. (Contains 3 tables and 8 notes.)