|Research has shown extracurricular activities to be positive contexts for youth development. Such activities have recently been conceptualized in terms of both breadth (number of activities) and depth (intensiveness of participation). However, relatively little is known about developmental changes in activity participation, whether such changes vary by activity domain (school, church and community), and whether intervening life transitions are associated with patterns of change. Moreover, there have been few examinations of selection factors (e.g., peer deviance and academic achievement) in relation to activity participation across development. The current study addressed these issues using data from an ongoing prospective longitudinal study of youth development (N = 428). To obtain the extracurricular activity measure a survey was administered in 7th and mailed out in 12 grade; intervening life transition measures were collected from the mother in 8th through 10th grade; and information on possible selection factors was collected either before or during the 7th grade. Findings indicated that breadth and commitment generally decreased through adolescence, while hours of participation increased. However, the pattern varied depending on domain (e.g., hours in school and church activities increased whereas hours in communities activities decreased). Negative life transitions were associated with declines in breadth of participation in school and community activities but increased levels of commitment to church activities. Early involvement in activities generally predicted later involvement. Selection factors (especially academic performance and peer deviance) also predicted participation, even after controlling for prior participation. The current findings add to the body of research on activity participation by documenting the multidimensionality of depth of participation (hours and commitment), and identifying moderators and selection factors of activity participation.