The influences of high school community service participation, extracurricular involvement, and civic knowledge on voting and volunteering in early adulthood were examined using the National Educational Longitudinal Study. The major finding in this study is that both voluntary and school-required community service in high school were strong predictors of adult voting and volunteering. In addition, involvement in high school extracurricular activities was predictive of voting and volunteering. Civic knowledge was related only to voting. The authors consider the findings for their policy relevance and their contributions to theoretical debates. (Contains 4 figures and 6 tables.)