Sustainable Energy for Developing Countries is the Academy's third research report in a series designed to examine critical science-related issues of importance both to the North and South. Developing and emerging economies face a two-fold energy challenge in the 21st century: Meeting the needs of billions of people who still lack access to basic, modern energy services while simultaneously participating in a global transition to clean, low-carbon energy systems. Both aspects of this challenge demand urgent attention. Developing countries themselves must take the lead in charting a new energy course. But developed countries must stand ready to provide support, recognizing that they have a vital stake in the outcome. Authors Dilip Ahuja and Marika Tatsutani provide a comprehensive assessment of how developing countries can meet both of these energy challenges within a broad strategy for sustainable economic growth.