Frequently, adults organize and implement youth projects without involving youth in the process. However, youth should be involved in problem identification and program design because they understand the needs of their peers and how to reach them effectively. This paper examines youth participation as a process for bringing about effective youth development. A literature review examines six areas that need to be developed during adolescence, youth problems that arise when developmental needs are unmet, and benefits of youth participation in projects. A "ladder" (R. Hart, 1992) of youth participation has eight levels: manipulation; decoration; tokenism; assigned but informed; young people consulted and informed; adult-initiated, shared decisions with young people; young person-initiated and directed; and young person-initiated, shared decisions. Three case studies illustrate youth participation principles. In 1992, Fundacion Esquel-Ecuador started Ecuadorian youth forums that have involved approximately 15,000 youth from low-income neighborhoods and other organizations; function regularly in four cities and at the national level; and have presented youth concerns to presidential candidates in the areas of education, work, violence, and poverty. In Mexico, the Gente Joven program recruited volunteers, aged 16-20, to promote sex education at outreach sites and to assist in production of program materials. A Bolivian nongovernmental organization that aids public schools helped youth who came from traditional cultures and spoke Aymara to organize Asociacion Estudiantil MINKA and provided leadership training to 25 youth. MINKA is promoting the value of indigenous culture in the schools, has organized cultural activities and educational events, and has helped to restore cultural pride through critical discussion. The case studies demonstrate that at higher levels on Hart's ladder, youth have more opportunities to develop needed competencies. (SV)