Uncertainty clouds the development of the concept of corruption in modern political discourse. Although it is widely assumed that the concept underwent a substantial narrowing of focus during the eighteenth century, the conceptual parameters of corruption in eighteenth century thought have yet to be fully explored. In broad terms, prior to the eighteenth century the concept of corruption could be said to have connoted the moral decay of the polity due to the incidence of 'self-interested' conduct. By the early nineteenth century however, corruption denoted less a moral failure in the polity, so much as the unwarranted intrusion of 'self-interested' private motives of a financial kind in the fulfilment of public, political office. Crucial to this shift of emphasis, I will argue, was the reconsideration of 'interest' in eighteenth century thought. In arguing so, I wish to complicate the conventional histories of 'interest' which have tended to emphasise its 'positive' role in Enlightenment thought. On this view, the positive evaluation of 'self-interest' was thought crucial to the rise of modern polities based on the pursuit of the common good (ie. the peace and prosperity of the populace under a sovereign state) incorporating a more coherent delineation of private from public domains. I will argue however, that Early-Modern and Enlightenment thought (c.1500-1800) was characterised by persistent doubts about the role of interest in morality and politics. Part of these doubts related to the diversity of interests, including self-interest, national-interest, factional or partyinterest. A crucial question this paper seeks to explore is where corruption features as a problem in the context of these manifold interests?