Das Projekt "Vereisung von Windturbinen" wird vom Umweltbundesamt gefördert und von Deutsches Windenergie-Institut durchgeführt. The main objective of the research program co-funded by the European Commission is the analysis of wind turbine operation under icing conditions within Europe. The increasing application of wind turbines in mountainous regions and In Northern Europe raised the questions which have been partly answered by the project's results: - Which weather conditions cause icing and at which sites do they occur? - Which types of ice accretion can influence wind turbine operation? -What are the influences on aerodynamics, loads, control system, energy output etc.? In order to catalogue ice endangered sites a questionnaire, which is available in English, German and Finnish language, has been distributed to concerned operators and manufacturers. Results from the inquiry have been evaluated in terms of occurrence of icing, types of ice and ice formation, as weil as locations around the turbines where thrown off ice fragments were found. A map of Europe is presented, including the reported icing events from several countries covering from a few days to some weeks of operation under icing conditions. The inquiry also proved the assumptions for ice loads developed within the project to be conservative. Influences of icing on wind turbine loads are discussed and recommendations given with respect to interested parties such as manufacturers, certifioation bodies and operators. This research program investigates most of the possible influences of wind turbine operation under icing conditions such as: - Ice loads. - Public safety (better knowledge of ice debris trajectories). - Prediction of energy loss. - Exploitation of ice endangered sites for wind energy application. Recommendations are given for manufacturers, certification bodies and operators concemed. The results and summary of the present knowledge was discussed during the BOREAS II conference and seminar and has been published as a 371 pages proceedings.