Book excerpt: Policing Prostitution examines the complex world of commercial sex in the late Russian Empire. From the 1840s until 1917, prostitution was legally tolerated across the Russian Empire under a system known as regulation. Medical police were in charge of compiling information about registered prostitutes and ensuring that they followed the strict rules prescribed by the imperial state governing their visibility and behaviour. The vast majority of women who sold sex hailed from the lower classes, as did their managers and clients. This study examines how regulation was implemented, experienced, and resisted amid rapid urbanization, industrialization, and modernization around the turn of the twentieth century. Each chapter examines the lives and challenges of different groups who engaged with the world of prostitution, including women who sold sex, the men who paid for it, mediators, the police, and wider urban communities. Drawing on archival material from Russia, Ukraine, Belarus, Latvia, Lithuania, and Estonia, Policing Prostitution illustrates how prostitution was an acknowledged, contested, and ever-present component of lower-class urban society in the late imperial period. In principle, the tsarist state regulated prostitution in the name of public order and public health; in practice, that regulation was both modulated by provincial police forces who had different local priorities, resources, and strategies, and contested by registered prostitutes, brothel madams, and others who interacted with the world of commercial sex.