An aeromechanical evaluation of large (over 1 Mw of nominal power) Horizontal Axis Wind Turbines (HAWT’s) is performed is this paper. The strategy is based on the combination of an aerodynamic module, which provides the three-dimensional pressure distribution on the HAWT’s blades, an a structural module which takes such pressure forces as input data in order to compute both, blade deformation and strain and stress distributions over the blade. The aerodynamic module combines the three-dimensional nonlinear lifting surface theory approach, which provides the effective incident velocity and angle of attack at each blade section, and a two-dimensional panel method for steady axisymmetric flow in order to obtain the 3D pressure distribution on the blade. Such pressure distribution constitutes the input data for the structural module, which is a finite element package whose output is the blade deformation and strain and stress distribution along the blade, as well as material induced fatigue. This methodology is applied to study a 50 m long blade able to provide a nominal power of 3 Mw. Key words: Wind turbine, aerodynamics, structural behaviour, numerical simulation, efficiency.