Many countries face the need to reform the regulatory frameworks governing their water and sanitation services to expand access, reduce inequalities and tackle environmental challenges. This working paper examines trends in the economic regulation of water and sanitation services, drawing on lessons learned from a range of institutional models, including regulation by contract, regulation by agency and self-regulation. It highlights policy and regulatory instruments aimed at reducing social and territorial inequalities in access to water and sanitation services. It also explores how economic regulatory frameworks can evolve to better account for growing environmental pressures. Finally, the paper identifies the need for further research and analysis, including the development of a statistically robust survey to benchmark the performance of different regulatory models and inform institutional and regulatory reforms.