Although it is difficult to make sweeping generalisations about attitudes towards social practice, few would disagree with the assertion that paying for sexual services has always been regarded as morally problematic. This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book has been divided into seven main chapters which combine contemporary theories of socio-spatial process derived from the work of geographers, sociologists and historians with case studies of how these processes shape the lifestyles of sex workers in very different contexts. The overview inevitably draws out contradictions evident in the historic treatment of prostitution, which, to a large extent, were a reflection of the unequal sex and gender relations characteristic of pre-modern and modern cities. Focusing on the ‘heterotopic’ potential of sites of sex work, the book considers the idea that new forms of sexual morality may be produced through the transgressive actions of prostitutes.