At the request of CMS, OIG conducted an audit of Medicare Part D Eligibility Verification Transactions (E1 Transactions). E1 Transactions, which contain PHI, are used by providers to determine a beneficiary's Part D eligibility or to determine the billing order when the beneficiary has additional drug coverage. OIG found that 25 of the 30 entities audited used E1 Transactions for potentially inappropriate purposes, including evaluating marketing leads and other marketing purposes. OIG made certain recommendations, with which CMS concurred, including that CMS should issue clear guidance regarding the proper use of E1 Transactions, and take appropriate enforcement action when abuse is identified.