Fast cargo/container ships with large bow-flare suffer from slamming in the North Pacific, in the North Atlantic, and off the Cape of Good Hope, and they may happen to be damaged in the bow region. To avoid these situations, reduction of ship speed and refuge from storms have been known as the best strategies. In rough seas, the speed cannot be reduced extremely from the viewpoint of steering. Hence the bow region of such ships should be designed so as to take slamming into account. The strength rule for the bow longitudinals is provided by the classification societies on the basis of their experiences of structural damage due to impact pressure. Recently, the present authors proposed a theory of slamming of ships among regular waves, and the impact pressure in the bow region can be calculated for various wave heights with the aid of this proposed theory. From the results, the critical wave height for collapsing of side structures can be obtained for the respective classification societies. On the basis of the present investigations, guides for bow-form design and ship handling in rough seas are proposed. Probability of bow damage of fast ships due to slamming can be estimated by making use of wave statistics.