Objectives: We examined the natural groupings of leisure-time physical activities (LTPA) among US adolescents and their correlates. Methods: Data came from the 1999-2006 NHANES, restricted to 3865 boys and 3641 girls 12-19 years old. Respondents were asked to report > 40 types of moderate-to-vigorous LTPA in the past month. Latent class analyses were used to identify natural groupings of the top 10 LTPA using the proportion of each activity's metabolic equivalents (METs) to total energy expenditure from all physical activities. Results: For each gender, 5 natural groupings of LTPA were identified. Among boys, they were basketball players and runners (72.8%), football players (9.0%), bicycle riders (7.5%), soccer players (5.8%), and walkers (4.7%). For girls, the 5 natural groupings in descending order were dancers/walkers/joggers (79.0%), aerobic exercisers (6.1%), swimmers (5.6%), volleyball players (4.9%), and soccer players (4.2%). The natural groupings of physical activities were also impacted by age, race, weight status, region, and season of interview. Conclusions: The natural groupings of LTPA reflect adolescent's preference and these activity patterns are likely shaped by their social and physical environments. Better understanding of common LTPAs and their natural groupings is useful in the design of effective PA interventions.