Long term fullscale measurements of a container ship (24, 000 t DW type) on the PNW (Pacific North West) course have been operated for 52 months. Measurements and recordings have been conducted automatically using an automatic RMS meter which was developed by the authers. For three items of pitching angle, rolling angle and wave bending stress of upper deck, the RMS values, the maximum peaks, the minimum troughs and the zero cross mean periods for 30 minutes have been punched out in every three hours. The environmental condition data by the favor of the ship's crew are to be studied comparing with those ship's responses. In this first report, the authers have studied the statistical distribution of the environmental conditions, and corresponding operating conditions specially in rough seas. The number of data of the rough sea condition of wind velocity ≥40 kt or wave height ≥5 m, were about 400 among the 5, 200 total data.