The international tsunami symposium convened by the Tsunami Commission of the International Union of Geodesy and Geophysics was held during May 25-28, 1981 at Send ai, Of un a to and Kamaishi, North East Honshu, Japan. This symposium was organized by the Japanese National Committee for the Organization of International Tsunami Symposium, 1981. The opening and closing ceremonies of the symposium were held at Sendai and Kamaishi, respectively, and eight sessions at Sendai and two sessions at Of una to were arranged. About 140 scientists and engineers including accompanied persons from ten countries participated to make the symposium a great success. In all, 55 papers were submitted prior to the opening of the symposium, of which 54 papers being orally presented, were arranged in ten sessions: Tsunami source and earthquake, warning system Tsunami waves and spectra Tsunami potential estimation Theoretical arguments on tsunami waves Tsunami generation and numerical simulation of historical tsunamis Harbor oscillations by long waves and tsunamis (1) Tsunami run up Mitigation of tsunami hazards and socio-economic effects Harbor oscillations by long waves and tsunamis (2) Historical study of tsunamis. Besides, two special popular lectures were provided for about 800 citizens in the Sanriku coastal area at Of una to Nokyo Kaikan, where the 1960 Chilean tsunami caused great destructive damages. The title of the first lecture was on the 1960 Chilean Earthquake and Tsunami by Dr.