Males were more likely than females to participate in vigorous physical activity and strengthening exercises over the years 1997 to 2003. In 2003, 70 percent of males reported participating in vigorous physical activity and 60 percent reported participating in strengthening exercises, compared to 55 percent and 43 percent of females, respectively. In 2003, there were no significant racial/ethnic differences detected among male participation rates for vigorous physical activity, strengthening exercises, or enrollment in physical education class, while there were some differences among the females. A higher percentage of White females than Black females reported participating in vigorous physical activity, 58 percent versus 45 percent. Also, a smaller percentage of Black females reported participating in strengthening exercises compared to White and Hispanic females, 31 percent versus 46 percent and 44 percent, respectively.