The impact of participation in Youth Conservation Corps (YCC) on the personal and social development of youth is measured with the Psychosocial Maturity Inventory. In addition, informal observations are recorded by staff members and participants. Personal background information and pretest scores indicate that participants differ substantially. Three elements appear to be particularly important in determining the quality of YCC experience: the competence of staff; the nature of the work performed; and the organizational structure of the programs. Changes in PSM scores are limited to an increase in the Trust Subscale and a decrease in the Tolerance Subscale. (PJC)