The tsunami of May 23, 1960, originating in an area of profound crustal disturbance along the coast of Chile, resulted in the greatest natural disaster in Hawaii since the Aleutian-born tsunami of 1946. A study of T phases from earthquakes produced by this disturbance suggests that the duration of faulting responsible for the largest earthquake and the tsunami was about 7 minutes. With the exception of the Hilo Bay area, wave heights on the Island of Hawaii were generally low, ranging between 3 and 17 feet, and averaging 9 feet. At Hilo, the third wave, which developed into a bore as it entered the bay, rose 35 feet above sea level. The action of this bore is best explained in terms of an hydraulic shock wave; its relation to the tsunami wave train, however, is poorly understood. Patterns of wave heights on Hawaii's shores produced by recent tsunamis of diverse geographic origin are strikingly different, whereas those from nearly the same origin are remarkably similar. The city of Hilo, which experienced a loss of 61 lives and $20 million in property, sustained the most extensive damage that occurred in the Hawaiian Islands. The need for tsunami research and continual public education, as a means for preventing further disaster, is painfully evident. The wave height data presented, together with the fullest possible evaluation of the seismogram, should aid in indicating danger areas and forecasting wave heights in future tsunamis.