"Entering the Mainstream: The Quality and Extent of Online Education in the United States, 2003 and 2004" represents the second annual study of the state of online education in U.S. Higher Education. Supported by the Alfred P. Sloan Foundation, this year's study, like last year's, is aimed at answering some of the fundamental questions about the nature and extent of online education: (1) Will online enrollments continue their rapid growth?; (2) Are students as satisfied with online courses as they are with face-to-face instruction?; (3) What role do schools see online learning playing in their long-term strategy?; and (4) What about the quality of online offerings--do schools continue to believe that it measures up? The survey analysis is based on a comprehensive nationwide sample of primary campuses for all active United States postsecondary degree granting institutions that are open to the public. An appendix is included. [For the "Sizing the Opportunity: The Quality and Extent of Online Education in the United States, 2002 and 2003", see ED530060.]