The present paper relates to some model experiments and ship correlation in respect to manoeuvrability, carried out at the Osaka University Tank under cooperation of Kawasaki Dockyard Co. and Sasebo Heavy Industries Co. The standard zig-zag tests were carried out for a 12, 000 DW cargo liner and her model at various load condition, while the similar tests as well as turning and spiral tests were done for a 130, 000 DW super-tanker and her model at full load condition. These correlative studies show that model ships are much more stable on course, much quicker in response to helm and have less turning ability for slight helm, compared with actual ships. The difference between models and ships, however, decreases with increasing the intensity of turning motion, so that there is no significant discrepancy between the two in respect to turning diameter for hard over helm. In a word, there is a considerable model-ship disagreement upon stability on course, but not upon turning performance at hard over. It should seem that this discrepancy relate largely to difference in propeller race intensity through rudder effectiveness and possibly propeller fin effect. The difference depends upon the lack of friction correction for free-running models.