In 1957, the author analysed the structure of climatic boundaries in central Japan, The following is an outline of the method used. a. Three hundred and sixty-five precipitation charts plotting the daily precipitation for 1955 (scale 1 : 1, 500, 000); b. Twenty-four charts plotting boundary lines between the precipition and non-precipitation areas, half-monthly for the year ; c. Recording, in areas 15 km × 15 km, the concentration of the boundary lines, half-monthly throughout the year ; d. Plotting lines of the heaviest concentration there by determing the climatic boundaries for each half-month ; e. Plotting on one chart the climatic boundaries for each half-month ; f. Recording, in areas of 15 km × 15 km, the lines of heaviest concentration thereby determining the climatic boundaries for one year. The author, in this late treatise, applies the same method to the northern and southern regions of Japan, thus completing the climatic boundary chart for the whole of Japan. Illustrations Figures 1, 2, 3 & 4 are examples of the charts made to determine the climatic boundaries. for each half-month. Figures 5 & 6 show the half-monthly. climatic boundaries, of each region, for the year. Figures 7 & 8 show the climatic boundaries, of each region, for the whole year. The chart plotted in Figures 7 & 8 bears close resemblance to the winter charts, thus demonstrating that the climatic boundaries of the winter months are most marked while these of the summer months are hardly determinable.