This report presents the results of a short-term, longitudinal study of 176 high school students that extends and clarifies earlier cross-sectional studies of the likely costs and benefits of part-time employment to adolescent development. The earlier studies of employment concomitant with full-time school attendance indicated three general issues warranting longitudinal investigation: the impact of working on the development of responsibility, the impact of working on involvement with and commitment to nonwork activities and relationships, and the impact of working on the socialization of several less-than-desirable attitudes and behaviors. In general, the longitudinal and cross-sectional findings converge in all three areas. Specifically, (a) working facilitates the development of personal responsibility (i.e., self-management) but not social responsibility (i.e., concern for others); (b) the benefits of working to the development of autonomy are substantially greater for girls than for boys; (c) working diminishes involvement in school, family, and peer commitments; (d) working leads to the development of cynical attitudes toward work and the acceptance of unethical work practices; and (e) working leads to the increased use of cigarettes and marijuana. On , balance, it appears that proponents of the earlier and more deliberate integration of adolescents into the work place have overestimated its benefits and underestimated its costs.