A detailed design study has been carried out to determine design wave conditions in the Port of IJmuiden, the Netherlands. As the harbour basin of IJmuiden has a length of about 4 km, the effect of local wave growth by wind cannot be neglected. In this study a method has been developed to combine the effects of wave penetration and local wave growth. Wind waves were computed using the SWAN model of Delft University of Technology. This project was carried out jointly with BMT ARGOSS.