Vertical axis wind turbines (VAWT) have many advantages over traditional Horizontalaxis wind turbines (HAWT).One of the more severe problem of VAWTs are the complicated aerodynamicbehavior inherent in the concept. Incontrast to HAWTs the blades experience varying angle of attack during its orbitalmotion. The unsteady flowleads to unsteady loads, and hence, to increased risk for problems with fatigue.A tool for aerodynamic analysis of vertical axis wind turbines has been developed.The model, a Discrete vortex method, relies on conformal maps to simplify the taskto finding the flowaround cylinders. After the simplified problem has been solved with Kutta condition,using the Fast Fouriertransform, the solution is transformed back to the original geometry yielding the flowabout the turbine.The program can be used for quick predictions of the aerodynamic blade loads fordifferent turbines allowing the method to be validated by comparing the predictionsto experimental data from realvertical axis wind turbines. The agreement with experiment is good.