Around the world, the need for highly trained scientists and technicians remains high, especially for positions that require employees to have a college degree and skills in math, science, and technology. The pipeline into these jobs begins in high school, but many 'leaks' occur before young people reach the highly educated workforce needed to sustain leadership in science and technology. Students drop out of the educational pipeline in science and technology at alarming rates at each educational transition beginning in high school, but women and ethnic minority youth drop out at a faster rate. Women and minorities are consistently underrepresented in science and engineering courses and majors. They account for a small portion of the work force in high-paying and more innovative jobs that require advanced degrees. This schism between the skills necessary in our ever-changing economy and the skill set that most young adults acquire is troubling. It leads us to ask the question that forms the basis for this issue: Why are adolescents and young adults, particularly women and minorities, opting out of the math, science, and technology pipeline? The volume addresses gender and ethnic differences in the math, science, and technology pipeline from multiple approaches, including theoretical perspectives, a review of the work in this field, presentation of findings from four longitudinal studies, and a discussion of research implications given the current educational and economic climate. This is the 110th issue of the Jossey-Bass quarterly report series "New Directions for Child and Adolescent Development".