Current calculation methods of wave forces acting on the upright section of various types ofcomposite breakwaters, such as perforated wall caisson breakwater or the sloping top caissonbreakwater, are proposed mainly based on the hydraulic model tests. Since such model tests wereusually conducted by the limited design conditions, wave forces are not necessarily estimatedprecisely by these calculation methods. Recently wave forces are also investigated by numericalsimulations, however, it is still difficult to estimate the wave forces accurately especially for thespecial-type caisson breakwaters or the forces generated by the breaking waves.
　In this paper, the wave forces acting on the several types of caissons were investigated by thereview of the various experimental results conducted before, and the calculations based on thecurrent design methods. Major conclusions are as follows:
1) Since the Goda pressure formula overestimates the impulsive breaking wave force when thewater depth is large, the rubble mound foundation is high, and the wave height is relativelysmall, the modified water depth for calculating the impulsive pressure coefficient wereproposed in order to estimate the wave force accurately.
2) The calculation methods of wave forces acting on the sloping top caisson and the sloping topcaisson covered with wave dissipating blocks were investigated, and the minimum value of thewave force modification factors for the sloping top caisson with wave dissipating blocks isproposed.
3) The calculation method of wave forces acting on the perforated wall caisson were investigatedand the method to estimate the modified wave chamber width for calculating the impulsive forceon the rear wall of the wave chamber were described.