The regulation of prostitution is changing as rapidly as its organization and sex workers have had more influence on this than usually recognized in either theory or research on prostitutes' rights. Using examples from the UK, Australia, the Netherlands and New Zealand, the paper shows how elements of prohibition, legalization and decriminalization are variously adopted in response to specific interests and their political representation. With the focus on law reform, the impact of collectives is compared to that of other contemporary players in the politics of prostitution, including community groups, councils, the police and the sex industry itself. But attention is also paid to health and occupational initiatives, and the conditions promoting the self-regulation of sex work both by prostitutes and employers. The paper also argues that the role of collectives, together with changes in the wider regulatory context, reflect and reinforce increasing differentiation within prostitution.