In the context of burgeoning research on multinational corporations (MNCs) this paper addresses the issue of the representativeness of databases of multinational corporations (MNCs) in Ireland. It identifies some important deficiencies in existing databases much used by scholars in the field. Drawing on the international literature, it finds that this problem also characterises research on MNCs in many other countries. In the Irish context we find that the extant empirical research has generally excluded two key categories of MNCs, namely, (a) foreign MNCs which are not grant-aided by the main industrial promotions agencies and (b) Irish-owned MNCs. The paper outlines our experience in identifying and addressing these deficiencies in an effort to more precisely define the MNC population in Ireland, and more generally reviews some of the issues and obstacles confronting scholars investigating the MNC sector in Ireland and abroad.