Then, as now, society was fighting what has been characterised as an 'invisible enemy', though it is important to underline the period discussed here is well before the prelaboratory era, and Alexandre Yersin's discovery of the bacteria causing bubonic plague. 1 At the time pestilence and plague were seen in terms of infected air, rather than rats and fleas. Corrupt air, the cause and vehicle for the transmission of plague, was seen as constituting a poisonous substance generated by putrefaction of matter from bogs to insanitary conditions in cities. 2 Thus when individuals inhaled 'mal aria', it corrupted their bodily humours and plague was created within their systems, and then was spread to others through exhalation.This was a logical set of beliefs, which underlay not just medical theory, but also served to justify government policy against plague in renaissance and early modern Europe. It forms the background to this article, which examines the strategies to cope with plague in early modern Italy, hailed at the time and by historians as the country which provided the model for developing public health policies for other parts of Europe and later centuries. George Rosen, for example, in his classic study of the history of public health published in 1958 made an explicit connection between the achievements of the Italian Renaissance and developments in public health: 'the Renaissance is significant … because it is the dawn of a new period of history, the modern period, within which public health, as we know it, developed'. 3 These main strategies included cordons sanitaire, public health boards and substantial isolation hospitals known as Lazaretti. However, it is worth asking how far this heroic vision can be applied across a country, which was far from being a united kingdom, but rather a series of larger and smaller states. Each had different systems of government, which arguably might interpret and implement differently what contemporaries believed were the best measures to deal with plague. 4 Furthermore, how far were plague regulations actually enforced, given evidence of contemporary resistance? This also raises wider questions about whether it was human intervention or non-human factors, such as environment and climate, which determined the impact of plague in a particular area, a problem which has also been raised in relation to the third plague pandemic in the late nineteenth and early twentieth centuries. 5 This article does not pretend to answer these questions, but rather, by juxtaposing the recent and less recent historiography on mortality with that on public health in early modern Italy, seeks to raise questions about which plague measures contemporaries believed were efficacious, and how far evidence from more recent historical studies helps to justify those beliefs.