Interest group research has focused extensively on political access. While access does not guarantee influence, it is customarily seen as a crucial step towards gaining political influence. It is argued that groups with access are, all else equal, more likely to be influential than groups without access. Biased access may thus result in biased influence. On the basis of a review of this literature, the article shows how the concept of access rests on an intuitive understanding rather than an explicit definition. This hampers methodological discussions of measurement. We propose to define access as instances where a group has entered a political arena (parliament, administration, or media) passing a threshold controlled by relevant gatekeepers (politicians, civil servants, or journalists). On the basis of this discussion, we compare operationalisations based on our proposed definition with some of the major alternatives found in the literature.