In September 2016, the Federal Government introduced legislation to enable a plebiscite on same-sex marriage to be held in February 2017. It was subsequently voted down in the Senate and it is now unlikely that a vote will be held. Nonetheless, the debate surrounding the proposed poll placed a spotlight on the use of the plebiscite as a democratic device. One topic that warrants more attention is the constitutional and regulatory framework within which plebiscites operate. The Constitution does not contemplate plebiscites, and they are an unfamiliar presence in a parliamentary democracy that entrusts almost all law-making and policy decisions to elected representatives. There is, moreover, no standing legislation on how federal plebiscites should be run. This article examines how the ill-defined constitutional and legal status of plebiscites affects how they are initiated and conducted. It considers these issues in a general sense, but also analyses how they arose with respect to the proposed vote on same-sex marriage. It argues that the absence of express constitutional authority and established rules of practice means that federal governments face choices, and considerable uncertainty, about the most basic matters, including: the constitutional foundation of the vote; the use of compulsory voting; the consequences of a plebiscite if it is carried; the drafting of the question; the breadth of the franchise; the method of conducting the vote; and the rules around campaign information, funding and expenditure. The article suggests that long-term measures, such as standing legislation, should be considered, but that this should be preceded by a broader debate about the appropriate use of plebiscites within Australia’s constitutional arrangements.