If knowledge is a form of power, then to lack knowledge is to lack power, and to build knowledge is to build power. This seemingly basic notion is at the source of diverse streams of theory and practice entitled participatory action research, community-based research, counter mapping, popular education and empowerment evaluation. It is from these historical, political and methodological headwaters that a relatively new stream of work, called youth-led action research, evaluation and planning, arises. These practices, while distinct, all represent attempts to build the power and capacity of those at the margins of society to examine, define, and ultimately shape their worlds according to their needs, visions and values. Youth-led action research, evaluation and planning expands the social critique and progressive stance towards breaking the monopolies of power/knowledge to include age-based inequities, along with (and in relationship to) inequities based on race, ethnicity, class gender, sexuality and other markers of difference.