This article reviews trends, outcomes and issues in regulatory reform in OECD countries. First, it summarises the evidence on the evolution of regulatory environments and the economy-wide and sectoral effects of reforms (including privatisation) in both competitive and non-competitive industries in the past two decades. Turning to network industries, it then discusses the main policy issues raised by the need to adapt the regulation of the non-competitive segments of these industries to increasing competition in liberalised markets. It focuses on four topics that dominate the debate over regulatory reform: i) the move from command-and-control to incentivebased regulatory approaches relying on the removal of entry barriers in competitive markets, the adoption of price-cap mechanisms and the design of efficient and competitively-neutral charges for accessing the fixed networks of incumbents; ii) the pros and cons of structural measures such as privatisation, and vertical and horizontal separation of formerly integrated monopolies; iii) the ways to ensure that important non-economic objectives, such as universality of service, continue to be achieved in a more competitive environment at a minimum cost for society; and iv) the design of regulatory mechanisms and institutions that encourage best practice regulation.