Many examples of past breakwater failures show that the extent of damages results in the undular distribution. Such a fact has been pointed out in several papers and the authors named this character of dameges meandering damages of breakwaters. This phenomenon has already been explained from the point of view of non-uniform distribution of wave heights along a semi-infinite breakwater.
　In this note some examples of meandering damages of breakwaters in several countries are presented and the distributions of wave heights along breakwaters due to diffraction and mutual interference of incident and reflected waves are examined on the basis of calculations and model experiments. The non-uniformity of wave heights along the breakwater seems not to be ignored in the design of composite type breakwaters.