A longitudinal, artificial reef system is composed of a number of long submerged mounds, which are placed in the nearshore zone with the orientation normal to the shoreline. Incoming waves are refracted by the heads and longitudinal side slopes of these reefs, and thus their heights are enhanced for intensive wave breaking. A series of small scale model tests and numerical computations have been carried out to confirm the performance of the new reef system, which is found to be superior to the conventional lateral system. Wave heights around the reef system can now be estimated through numerical analysis. The present paper summerizes the findings of these studies for the purpose of providing the basic data for future development of prototype reef systems.