Findings indicated that youth demographic characteristics and school size differentiated between various types of activity participation. Of the six major portfolios identified, the Multiple Activity portfolio emerged as a unique and high functioning participator group. Adolescents in this group were mostly female, upper middle class, had the highest GPAs, the highest number of total activities, and were most likely to work for pay. Adolescents attending large schools who come from underprivileged backgrounds and who perform poorly in school warrant concern because these may be the very individuals who would benefit the most from activity participation. Hispanic adolescents were less likely to participate in school-based extracurricular activities. Future research should explore Hispanics and their activity experiences. In an attempt to understand the impact of extracurricular activity participation on adolescent development, most research has considered one type of extracurricular activity. Utilizing data from the National Longitudinal Study of Adolescent Health (Add Health), a large, school-based study of adolescents, their families, and their schools, this study examined and described adolescent extracurricular activity portfolios. It sought to identify the portfolios (combinations) of school-based activities in which adolescents participated and describe adolescent school-based extracurricular activity participation in regard to demographic, achievement, time use, and school-level characteristics. The six broad activity portfolios created were Sports Only, Academic Only, School Only, Performance Only, Multiple Activity, and Nonparticipation. Tables and references