A psychosocial conception of ego strengths is presented in relation to adolescent involvement in adult-sponsored structured youth activities. Five-hundred and seventeen high school students completed measures on their involvement in structured activities and on 8 ego strengths. Gender, age, and SES were controlled in a MANCOVA procedure and it was found that extracurricular activities of sports, student government, and belonging to an issues group, as well as engagement in volunteerism were related to several of the ego strengths. Religious attendance was not related to the ego strengths. In longitudinal analysis, it was shown that ego strength at Time 1 predicted involvement in structured activities at Time 2 (8 months later), but structured activities at Time 1 did not predict ego strength at Time 2. The findings are discussed relative to theory and research findings on the topic.KEY WORDS: adult-sponsored structured activities; positive youth development; ego strength.