Summary: The General Services Administration (GSA) awarded FTS2001 contracts to Sprint and MCI Worldcom to provide long distance telecommunications services to federal agencies. The federal government began the sizable and complex effort of switching from the existing FTS 2000 contracts to FTS2001 in June 1999. Several implementation issues have delayed this transition. One of these issues concerns the billing problems experienced by GSA and its contractors. GAO found that the billing problems often arose from changes in contracts and services. According GSA, these issues also arose from the differences between contractors' commercial billing practices and the government's practices. Because these billing problems were not promptly resolved, they had an adverse effect on the transition progress. GSA is taking steps to resolve current billing problems. It is tracking issues as they arise, and it is now trying to resolve 12 issues still outstanding with Sprint and MCI WorldCom, including the problem of commercial billing. In addition, GSA's Office of Inspector General recently began a review of the FTS2001 billing area, which might also identify ways to prevent future billing problems. Another issue that affected the transition progress concerns the databases that supported the transition process. GAO found that although GSA developed an automated system to track transition data and develop reports, the FTS2001 contractors did not furnish GSA with the data it needed to populate that management system's database. As a result, GSA and agency transition managers did not receive the timely and up-to-date information they needed to effectively plan and manage transition activities.