This paper revisits Mary Douglas' Purity and Danger: An Analysis of Concepts of Pollution and Taboo (1966). A survey of this theory in architecture in the late-twentieth century reveals how it focused attention on relationships between dirt, cleanliness, and the design and organisation of space—an area previously neglected in architectural thought. Dirt remains an important focus within architectural and urban theory, with implications for practice. Yet, the intersections that scholars of the 1980s and 1990s made between Douglas' work and critical theory, feminist and psychoanalytic writings elicited problems with her structuralist approach that remain unresolved. These are apparent in considering relationships between dirt and cities—indeed, the aphorism Douglas invokes, “dirt is matter out of place”, originates in discussions of nineteenth-century urbanisation. To better understand dirt's relationships with modern and late-modern capitalist cities, Douglas' insights can be productively read alongside post-structuralist accounts, including the psychoanalytic notion of the abject and recent neo-Marxian scholarship on the production of urban nature.