This special issue of Regulated Rivers contains most of the contributions presented at an international workshop on Remedial Strategies in Regulated Rivers, held in Lycksele, Sweden, 25-28 September 1995. The workshop was held under the auspices of the Swedish Environmental Protection Agency as part of the final phase of the Swedish research programme, Environmental Improvements in Regulated Rivers, which began in 1991. The research programme has been financed by Vattenfall, a power company responsible for half of Sweden’s hydropower production, and the Swedish National Board for Industrial and Technical Development. The Swedish Environmental Protection Agency has been responsible for the administration of the programme and the scientific evaluation of the projects. The Norwegian Water Resources and Energy Administration and the Swedish World Wide Fund for Nature provided additional funding for the workshop, while Vattenfall organized an excursion to a regulated river, Umealven. We wish to thank all the scientists who kindly agreed to participate in this workshop and thus enabled us to benefit from their knowledge and experience in the field of remedial measures. About half of the electricity in Sweden is produced by hydropower; the other half by nuclear power. Most of the largest hydroelectric power stations in Sweden were built prior to 1970. At that time environmental considerations were not given high priority. However, from the 1960s onwards, environmental awareness has grown and in 1987 a number of rivers were protected from hydropower development. In 1993 further river sections were protected and the four large, free-flowing rivers, Tornealven, Kalixalven, Pitealven and Vindelalven were designated as ‘National Rivers’. However, the decision to phase out nuclear power by 20 10 has increased the pressures for more hydropower. There are now opportunities for improving environmental conditions in existing schemes and this has led to co-operation between environmental authorities, the hydropower companies such as Vattenfall and the National Board for Industrial and Technical Development in order to find appropriate solutions. The present research programme and workshop are evidence of this growing co-operation in river management. Hydropower development, as with most forms of energy production, has an impact on the environment. The workshop has, however, clearly shown that there are also strong international efforts to ameliorate these effects through the employment of remedial measures. Nevertheless, the range of solutions is still rather limited and their long-term sustainability has only been demonstrated in a few cases. Further work on remedial measures is obviously needed, both basic ecological understanding of individual measures and an appraisal of their practical, long-term function in a catchment context. This calls for increasing co-operation between those responsible for regulation, government agencies, engineers and environmental scientists.