The Alfred P. Sloan Foundation is closing its online-education grant program, and some college officials are concerned that the decision will leave a fast-growing sector of American higher education without a major source of support. The New York City-based foundation has funneled roughly $80-million into online-education ventures around the country since the early 1990s. The philanthropy's impending withdrawal has aroused anxiety about what will fill the vacuum. In a telephone interview, A. Frank Mayadas, program director at the foundation, credited Sloan's efforts with spearheading "a revolution which forever will change education." But foundations "are not in the business of sustaining things," he said. "Foundations are in the business of starting new things." Mayadas described the program as "effectively closed," since the grants being made now "are almost exclusively already in the pipeline." Although there seem to be relatively few grant opportunities for online education by itself, Mayadas and university officials hope that a range of future options, from federal agencies to corporations to other foundations, will step into the gap created by Sloan's exit.