The objective of this project 'OPHWT' is to develop an efficient numerical code, for the optimisation of the aerodynamic characteristics of horizontal axis wind turbines. A vortex model has been treated based on the lifting line theory. The circulation at the trailing edge is obtained by resolving the variational problem; consisting in find the optimal circulation on the lifting line of the wind turbine, by minimising the losses due to the induced velocities. The value of the circulation is further updated by virtue of a multiplicative factor obtained by maximising the torque. Confrontation of the results obtained with those of Maekawa, Sharpe, a Glauert's blade element momentum theory calculations and a developed simplified model, have revealed the potential of the optimum project in predicting improved and higher rotor performances. (c) 2005 Elsevier Ltd. All rights reserved.