The mathematical-hydrodynamical considerations on the wave resistance of ship-shaped bodies present, in this writer's opinion, the most interesting problems met in theoretical Naval Architecture. The first experimental towing tanks were designed primarily for research on this aspect of ship resistance. A tremendous amount of experimental work has been done, the data on which are available in the transactions of the many engineering institutions. The goal, to express the wave resistance of a ship as a function of its shape, has nevertheless not yet been attained by the experimental method. On the other hand it cannot be denied that systematic model testing is the most important method of approach when considering improvements in the resistance characteristics of a ship.