Many Netherlandish towns and cities in the fifteenth century had to deal with recurring public health crises. 1 Struck by outbreaks of the plague and famine, this strongly urbanised region -at the time over a third of the population in Flanders, Brabant and Holland lived in cities -faced significant challenges (Unger, 1999: 329-330; Blockmans, 1980: 43, 46;Stabel, 1997). 2 Sint-Truiden, a relatively small, yet significant market town situated in today's Belgian Limburg and the site of a large Benedictine abbey since the seventh century, fared little better. Three types of health-related crises struck its community between 1417 and 1490, at the time numbering between 4.000-6.000 inhabitants: famine, plague and financial hardship as a result of falling population numbers. How did the city handle these exigencies? This chapter will argue that, in response, the city pursued vital politics by maintaining porous boundaries. It modulated the intake and output of food, persons, matter, and, by extension, money, to uphold balance and motility in the circulation of goods, energy and waste (Rose, 2007;Hoffmann, 2007;Kaye, 2014;Knoll -Reith, 2020). In this way the weekly bylaws issued by the city magistrates actively anticipated and responded to the biopolitical challenges of managing the urban body politic on a population level, to ensure its vitality. In doing so, they built on existing practices, infrastructure and knowledge as well as adopting new policies.Before turning to the city of Sint-Truiden in more detail, it is necessary to briefly discuss some key ideas and developments in the field of public health and environmental studies relating to this period. This chapter will, therefore, commence by introducing a few concepts and interpretations of health policies, before exploring Sint-Truiden's strategies in more detail.