The problem of bats and wind farms is first described. Then guidelines for an assessment methodology are developed in order to take account of this problem in planning schemes. During the studies a distinction between two populations can be made: local and migratory. The local population are those animals present during the breeding period; migratory animals are those, which, especially in early and late summer, and autumn, undertake transfer flights. In doing so, they are killed in significant numbers by wind turbines. For the study we recommend a combination of methods, the bat detector and the “automatic bat registration box”. In woodland areas we also recommend mist-netting to evaluate impacts due to the siting and construction of wind farms. In all current research methods, the flight activity of bats at altitudes of more than 100m is virtually unknown – so that here is a special research need. Bat behaviour is different during the summer and the migration period, so the results have to be evaluated and presented separately. Different ways to reduce the impacts are shown. Finally, so that future planning can take this problem into account, we describe fields of research which are urgently needed.