The International Atomic Energy Agency (IAEA) together with the Hungarian Atomic Energy Authority organised a regional workshop on Regulatory Control Effectiveness in Energy Market Deregulation between 29 March – 2 April 2004 in Budapest. The workshop was attended by 15 staff members of nuclear regulatory authorities from 7 countries of the East-European region. Lectures were given by the experts of IAEA, UK, USA and Hungary. The workshop gave an opportunity for exchanging information on different national experiences that arise from the regulation of nuclear power plants in a liberalised electricity market. Different methods were discussed on how to maintain the effectiveness of the nuclear regulatory bodies and how to ensure nuclear safety of the NPPs in the changing environment of a deregulated energy market.