This essay explores the idea of ‘bio-politics’ in relation to the modern city. The concept is traced through its original Foucauldian formulation to more recent explorations of the relationship between the body and the city. We explore the idea through the emergence of discourses on hygiene, public health and differing conceptions of ‘urban order’. We find that the bio-political dynamics of urban space encompass both juridical and dispersed sources of power in modern societies. It is concluded that existing conceptions of power in urban space need to take account of those diffuse sources of power that enable the modern city to function in spite of its contradictory dynamics. We also need to contend with those ‘zones of indistinction’ which appear to lie outside conventional urban discourse yet reveal much about the hidden dimensions of urban modernity.