An overage tanker “ERIKA” was wrecked in 1999 at rough sea off the coast of Brest in France. In consequence of the marine disaster, a large quantity of heavy oil spilled into the sea from the wrecked tanker and all over the coast of France was heavily polluted. In such a case, she should be towed immediately to a safe place to avoid a secondary calamity and minimize the marine pollution. We had a similar marine disaster in the case of Russian tanker “NAKHODKA” which was wrecked in 1997 at the Japan Sea. However, there has been no study of methods for stable towing or of maneuvering motion during the tow of wrecked tanker's fore part. Whenever we encountered such a marine disaster, we have been relying upon our experience and intuition in the towage of wrecked tanker. In this paper, unstable motion and course keeping ability of tow and towed ships at rough sea have been examined as a first step by using measured hydrodynamic forces acting on a tanker model of which fore part is wrecked.