Recently the superstructures of train ferries are made gradually larger, consequently the manoeuvering becomes difficult or sometimes even impossible in Aomori-Hakodate line, where the strong winds blow in winter. The train ferries need regular arrival and deperture in order to perform their service, so they are required the high manoeuverability. To satisfy this requirement, we must make clear the effects of wind on the manoeuverability of train ferries and find the measures for reducing or preventing that harmful effects. Many able researchers have studied on the directional stability and the turning motion of vessels, and it seems that some of them have attempted to obtain the relation between the directional stability and the turning motion but none has been successful in his attempt. Notwithstanding the fact that the nature of directional stability or turning motion has been made clear to some extent, we have not been able to consider the problem of manoeuverability for practical cases. For instance, it has been said that the manoeuvering of trawlers and drifters is difficult under strong winds, but this subject has not been analysed and has not been able to discuss in detail. The author supposed that a vessel will take a stable course and advances on this course after a long time, and that she may be said to be manoeuvered when she is possible to turn to both sides. Then the author considered the steady motions of a vessel and investigated their stability; by this study the relation between the directional stability and the turning motion was made clear, and it became possible to discuss the effects of wind on the motion and manoeuverability of vessels. In this paper, applying these results, the author discussed this subject on the case of train ferries. The results obtained from this study are as follows. (1) The train ferries has the tendency to turn windward except in the case when the strong adverse wind blows diagonally. This tendency agrees with the actual experiences in Aonzori-Hakodate line. (2) The manoeuvering is possible at high speed and becomes impossible at low speed as compared with wind velocity. Namely a train ferry will be in the following ranges according to the value of wind velocity/ship speed: (i) When the wind blows diagonally from behind, (a) the range where she is manoeuverable, (b) the range where she turns windward. (ii) When the adverse wind blows diagonally, (a) the range where she is manoeuverable, (b) the range where she turns windward, (c) the range where she is manoeuverable, (d) the range where she turn leeward. (3) To widen the range where the manoeuvering is possible, the following are effective: (a) To make smaller the force by the wind and the moment by the wind blown diagonally from behind. (b) To make larger the moment by the adverse wind blown diagonally. (c) To enlarge the effectiveness of the rudder. (d) To make directionally stable, namely to trim by the stern and to attach dead wood to the stern. The above results were obtained for train ferries. Some kinds of vessels may have the opposite tendency. Still there are many unknown factors, so this subject must depend upon the further experimental studies.