Abstract: Verification and validation has been the key problem to the development of CFD. The AIAA CFD Drag Prediction Workshop (DPW) Series was an important academic activity concerning verification and validation of CFD, whose purpose is to provide an impartial international forum for evaluating the effectiveness of CFD Navier-Stokes solvers, and to assess state-of-the-art CFD methods as practical aerodynamic tools for the prediction of forces and moments on industry-relevant geometries. The results and conclusions of the four DPW series are summarized. Finally, some thoughts are put forward with respect to the development of CFD.