The Aleutian-born tsunami of March 9, 1957, produced water heights on the island of Hawaii between those produced by the 1946 and 1952 tsunamis. The tsunami-generating mechanism, although poorly understood, permits a hypothesis of multiple waves generated near the source (or the same wave traveling different paths) which eventually interfere to produce contrasting intensities in different parts of the broad Hawaiian area. Comparisons suggest that each tsunami is unique and unpredictable in some respects and predictable in others. Water heights depend in part on location and orientation of coastlines with respect to the earthquake epicenter and the presumed line along which the tsunami was generated. Local conditions of seiche and coastline configuration further modify average wave heights. Local conditions are effectively constant with respect to Aleutian tsunamis, and empirical data on water heights and danger areas are available. A program of improving tsunami and earthquake observations, together with additional tide-observation stations, may eventually permit more precise evaluation of a tsunami both before and after its arrival.