We considered the motion of a ship with two degrees of freedom—pitch and roll—when secondorder, static couplings are included in the equations of motion, and we obtained a nonlinear analysis of the response of the ship to a harmonic excitation (i.e., a regular sea) using the method of multiple scales. In the first part of the paper, we considered the pitch frequency to be twice the roll frequency and found that a superharmonic response exists for any value of the amplitude of the excitation, but a subharmonic response is possible only if the amplitude of the excitation is above a critical value. In the second part of the paper, we considered ships without the two-to-one frequency ratio. We found that there are five resonant situations and, depending on the value of the parameters, three can involve large motions. Some of the present results were combined with some results from a previous paper to determine the variation of the amplitude of the response with the encounter frequency. Also, the accuracy of some of the present results was established by comparing them with a numerical solution.