[en] Ensuring public health and safety has been and will continue to be the cornerstone of nuclear power regulation. Economic factors, deregulation, technological advancements and government oversight are some of the elements that are leading regulatory bodies to review their effectiveness. Seeking to enhance the present level of safety by continuously improving the effectiveness of regulatory bodies is seen as one of the ways to strengthen public confidence in the regulatory systems. The first step taken by the NEA Committee on Nuclear Regulatory Activities (CNRA) was to hold in June 1999 an international workshop on 'Developing and Measuring Regulatory Effectiveness'. The main objectives were to improve knowledge about regulatory effectiveness in relation to nuclear installations, to establish a better understanding of how regulatory effectiveness may be measured, and to share experience in enhancing regulatory effectiveness. A key conclusion was that more effort is needed regarding communication issues and how the regulator can best establish and maintain a dialogue with the public. The issue of maintaining a dialogue with the public was addressed in a second international workshop organised by the CNRA in November 2000 on 'Investing in Trust: Nuclear Regulators and the Public'. Other issues such as internal quality assurance, the continuing need for international exchanges among regulators to ascertain whether regulatory effectiveness can actually be measured and provide meaningful results, and the concept of regulatory independence were also regarded as significant issues. In order to address these and other issues. the CNRA set up a task group of senior-level regulators to take an in-depth look at the basic concepts underlying regulatory effectiveness, advances being made and future requirements. (authors)