Breakwater design at this moment is based on physical scale modelling combined with the use of experimental design formulae. These formulae are all derived from scale model tests together with simplifying the theoretical assumptions. Several breakwaters failures in the past indicate that the state of the art on this subject suffers from a significant lack of full scale data which could give rise to safer design standards. Within the MAST II framework of the EU (Marine Science and Technology), Ghent University has coordinated a research project, involving different partners from all over the EU, of which the primary goal was to collect full scale data on breakwater behaviour under wave attack, namely at the Zeebrugge NW Breakwater at the Belgian coast. Flanders Hydraulics, the hydraulic research laboratory connected to the Ministry of the Flemish Community, has taken part in the project, namely in conducting physical scale model tests parallel to the full scale measurements on site. This article describes these tests and summarises some important results concerning wave runup, wave setup and wave forces on armour units.