The growth in size and fullness of oil tankers and other crude carriers has come to a standstill for the time being, but no one will ever think it has reached its final limit. In contrast to this growth, the prediction of full scale performance of ships from model test results seems to have been losing accuracy and reliability. DAIOH was built as a 1/15 scale model of a prospected 460, 000 DWT tanker and was tested on the sea so as to ensure more reliable prediction of ship performance. Resistance and propulsion test results seem to be successful. Tests of small models similar to DAIOH were also carried out at indoor model basins but they yielded rather considerable scatter of data, so that the scale effect upon resistance and self-propulsion factors have not been fully investigated. The authors think, however, that this disappointing results might have something to do with the inherent nature of this particular hull form or otherwise with the model testing technique of today.