This paper presents the results of theoretical evaluation of motions, shearing forces and bending momets of a destroyer in regular head seas. The calculated values of heave, pitch and midship bending moments have agreed with the experimental values of model tests. The obtained conclusions are as follows: (1) The damping coefficients for the heaving and pitching motions are extremely large, and the conpling effects between heaving and pitching are very large, compared with the merchant ships. (2) When the wave creast or the wave trough passes near the midship, the largest bending moment occurs at the position near the midship, and the largest sharing forces occur at the positions distant about 25% of ship length from midship, fore and aft. (3) The value of (ware length/ship length) ratio, at which the amplitudes of bending moment and shearing forces mentioned above in (2) reach maximum values, is between 0.75 and 1. (4) The maximum bending moment in high speed is nearly equal to the statically calculated value with Smith effect.