The geography of the regulation of sex work in colonial Hong Kong is examined as a contribution to the historiography of the colonial city. Particular attention is paid to racial and sexual segregation and their relation to Foucauldian concepts of discipline and regulated sexuality. The introduction and revision of Venereal Disease Ordinances, and the landscape of regulated prostitution that resulted, are read as part of a mid-nineteenth-century crisis of government. Ultimately, the political and discursive construction of Chinese racial/cultural difference reveals the limits of ‘imperial governmentality’ as much as the ambition of colonial sexual discipline.