Newton, Mass.--The U.S. business Internet service provider market will grow to $63 billion and provide higher margins than the "cutthroat" consumer segment, according to a new report released by Cahners In-Stat Group. In 1999, the major business ISPs are experiencing revenue growth of nearly 100%, according to Cahners In-Stat Group analyst, Kate Von Goeler, who also said MCI WorldCom/UUNet is the clear industry leader but is being challenged. New business ISPs are gaining by serving small and midsize enterprises. Other upstart ISPs are focusing on value-added services to take business from incumbents, according to Cahners. The report, "Big Business: Rankings & profiles of the top U.S. ISPs serving the enterprise, 1999," examines the total U.S. business ISP market and provides forecast data.