The 109th Congress is examining the role of groups organized under section 527 of the Internal Revenue Code (IRC) that are involved in federal elections but are not operating under the requirements and restrictions of federal election law. Although such groups only recently emerged into public awareness, in 2004, they were widely seen as major players in the presidential election, with more than $400 million spent seeking to influence the outcome. Strictly speaking, the term “527” refers to a section of the Internal Revenue Code, which was added in 1975 to provide tax-exempt status to federal, state, and local political organizations, as defined in that statute. The controversy over these 527 groups arises from two factors: the different definitions used in federal election law and tax law as to what constitutes election-related activity and, further, the lack of certainty as to what election law itself regulates or may permissibly regulate. This report discusses these groups in detail, as well as related legislation.