Aeroelasticity is a key issue in the continuing development of wind turbines towards large, flexible, highly optimized machines. The steadily increasing technology level is reflected not necessarily by the complexity of the turbines, but by the level of knowledge and advanced principles that are taken into account during the design process and incorporated in the final optimized design. This article examines some of the main uncertainties within aeroelastic modelling of wind turbines that have been hard to resolve over the years of research, and also presents perspectives for the new aeroelastic challenges, both from the viewpoint of the researchers at Riso National Laboratory. Copyright (C) 2003 John Wiley Sons, Ltd.