The Ship Research Institute is conducting a long-range research project to evaluate present methods of ship structural design and to suggest improvement based on a more realistic knowledge of the loads, stresses and motions which ships experience in service. The papers on the results of experiments on general cargo boats in North Pacific Ocean were reported already. The tests on large tankers started several years ago and the measurement of ship motions, deck longitudinal stresses and transverse stresses in flange plate of bottom trans in ballast water tank has been carried out on several large tankers. This paper discribs the outline of the tests and presents the data in some detail in order to expedite their use by other investigaters. During the entire tests, the maximum magnitude in ship life of about 20 years were estimated 2530 kg/mm² in double amplitude in deck. The transverse stresses in ballast water tank were not severe compare to the statical stress due to loading in still water.