"Online Nation: Five Years of Growth in Online Learning" represents the fifth annual report on the state of online learning in U.S. higher education. This year's study, like those for the previous four years, is aimed at answering some of the fundamental questions about the nature and extent of online education. Supported by the Alfred P. Sloan Foundation and based on responses from more than 2,500 colleges and universities, the study addresses the following key questions: (1) How many students are learning online?; (2) Where has the growth in online learning occurred?; (3) Why do institutions provide online offerings?; (4) What are the prospects for future online enrollment growth?; and (5) What are the barriers to widespread adoption of online education? Additional tables and charts are appended.