The importance and benefits of regular physical activity to enhance health and reduce risk of all-cause mortality have been reported (Centers for Disease Control and Prevention, 1997; U.S. Department of Health and Human Services, 1996, 2000). With recognition of the benefits of physical activity, promoting health through regular physical activity has been emphasized and is a national health goal for all ages. It has been recommended that the critical time for adoption of physical activity behaviors is during adolescence (Morrow, Jackson, & Payne, 1999). Information about adolescents’ physical activity habits including their preferences and physical activity levels can be used by schools to develop curriculums and by community organizations to plan physical activity programs to promote lifelong physical activity. The purpose of this study was to examine adolescents’ physical activity behaviors. In this study, data from the 1999-2000 National Health and Nutrition Examination Survey (NHANES) were analyzed to examine following main questions: (a) How much time do they participate in moderate and vigorous physical activities (MVPA)? (b) Which physical activities do adolescents frequently engage in? (c) Are there gender differences? Data from 1147 adolescents (572 boys and 575 girls) aged from 12 to 15 years old (M = 13.9 years, SD = 1.1) were analyzed. The data on MVPA were collected during the 30 days preceding the survey. Using a MANOVA, gender differences on VPA and MPA were examined. There were significant differences in physical activities between boys and girls, Wilk’s lamda = .964, F (2, 1144) = 21.66, p < .001. Univariate analysis of variance revealed that boys participated in more VPA than girls, F (1, 1145) = 43.07, p < .001. Interestingly, 18% of boys and 36% of girls engaged in MVPA for less than 10 minutes per day while 35% and 56% of boys and 20% and 35% girls engaged in MVPA for 60 and 30 minutes per day. The three most frequent VPA were running (24%), basketball (23%), football (15%) for boys and running (28%), basketball (12%), and soccer (6%) for girls while, the three most frequent MPA were bicycling (14%), walking (12%), and basketball (11%) for boys and dance (18%), walking (18%), and bicycling (9%) for girls. The results of this study demonstrate a need to address strategies to encourage participation in regular physical activities among sedentary adolescents, especially girls. Schools, public health agencies and community organizations should provide more lifetime physical activities for girls.Keyword(s): health promotion, physical activity, youth sports