In this paper the results of systematic steering experiments tested with self-propelled, free-running ship models are described. These three models, 2. 50 metres in length, are selected each corresponding to three representative normal types of present-day vessels, namely, a high speed liner, a cargo ship and a super tanker. Experiments are carried out mainly to get informations on basic design problem such as on optimum rudder area. Together with effects of hull form and relative rudder area, those of rudder angle, speed, trim, displacement, turning side, etc. are also investigated.