As first reported by the Medical Group Management Association (www.mgma.com), last week an official at the Centers for Medicare and Medicaid Services (CMS) reported that the agency identified a significant problem with the Medicare Ordering and Referring File. This file contains the National Provider Identifiers (NPIs) and the legal names of all physicians eligible to order and refer in the Medicare program and who have an enrollment record in the Provider Enrollment, Chain, and Ownership System (PECOS). Some 48,774 physicians were incorrectly left off the list, and CMS has indicated it has now added these physicians to the updated list on the CMS Web site. This error may explain any recent inaccuracies with the list, and MGMA says it encourages you to check the updated Ordering and Referring File to ensure that your physicians are listed. This problem illustrates some of the difficulties practices face when verifying whether physicians are in PECOS and the frustrations they have with the overall Medicare enrollment process.