Research on modern red-light districts (RLDs) is deficient in some key respects. Centered largely on street prostitution zones and nations where prostitution is illegal, this literature gives insufficient attention to settings where RLDs consist of a cluster of indoor venues that are legal and regulated by the authorities. Using classic Chicago School research on vice districts as a point of departure, this article examines the physical structure and social organization of red-light zones in two Belgian cities: Antwerp and Brussels. The comparative analysis identifies major differences in the social ecology of the two settings. Differences are explained by the distinctive ways in which each municipal government manages its respective RLD, which are related to the contrasting social backgrounds and political capital of the population residing in the vicinity of each district. Policy implications are briefly discussed.