The city and harbor of Hilo, located on the northeast coast of the island of Hawaii, have been severely damaged by numerous tsunamis. Physical features which play an important role in the formation of tsunami bores at Hilo are the submarine ridge formations in deep water outside the bay mouth and the nearly vertical cliffs along the Hamalcua coast which reflect the tsunami wave into the harbor. The purpose of this paper is to discuss the Hilo Harbor Tsunami Model and this reflected wave and its effects. The tests described and the resultant information presented herein, unless otherwise noted, were obtained from research conducted under the Hilo Harbor Model Study of the United States Army Corps of Engineers by the Honolulu Engineer District. The permission granted hy the Chief of Engineers to publish this information is appreciated.