This paper describes summarized results of comprehensive study on monitoring of hull responses. Based on the experiences from development and onboard test of monitoring system, investigations are made in significance of monitoring, measured data of hull responses, functions of monitoring system, items and alarm level of hull responses, etc. Results obtained are as follows : (1) Monitoring system should be needed for prudent seamanship in rough seas and for verification of new design procedure, and this system may have functions of direct monitoring and recording of hull responses. (2) As for peak value of deck stress, compressive stress is fairly larger than tensile stress in car carrier. On the other hand, tensile stress is rather larger than compressive stress in bulk carrier. These results are good correspondence with calculation by nonlinear strip theory. (3) Main role of monitoring system is to offer correct information on hull responses rapidly to the officer. Monitorings are generally to be done on vertical acceleration at bow, deck stress at midship and horizontal acceleration at bridge. (4) Alarm level of hull responses should be set as a standard for prudent seamanship. Hull damages will be reduced by prudent navigation and operation of ships together with verification of rules and standards.