Notorious for its ravaging climate in winter, the North Pacific is feared among seafarers as theldevil's water. In the past 10 years, it ran havoc with many large vessels and took many lives and much property. So, the Japanese Ministry of Transport has conducted a research project for five years since 1982 to clarify the effect of wave force on hull and develop Computer Aided Navigation System for Safety (CAN). This is 'a kind of shipboard instrumentation system for the sensing of incident waves, ship motions and structural responses and prediction of response changes to be expected when ship's course or speed is altered. This system was installed on a container ship “Japan Alliance” operating in the North Pacific service and checked its functions and performance. During the experiment, from 1986. 11 to 1987. 1, significant full-scale data on ship motions, vertical accelerations, bending moments etc. were obtained. Report here is a presentation of the experimental results on the Computer Aided Navigation System for Safety.