In 1957 the national forest of Japan adopted the sampling method for forest inventory. Two years after that, the result of such an inventory compared with the value so far obtained, gave a volume of 122 per cent and a growth of 173 per cent of the method used so far. Apart from the volume, the significant increase in the estimate of the growth raised a controversial problem and in 1959, six regional forestry offices in the country examined the accuracy of the survey on the growth by use of increment borers on the important species. The outline of this investigation is described in the following section. Because the writer obtained the data of this investigation only recently, the statistical examination of them could not be made before the submission of this paper. The conclusions we made in this paper do not differ much from those of the statistical test. For one part of the design consultation was made with staff-members of the Government Forest Experiment Station. The final design was made by members of the Planning Section of the Forestry Agency. Unfortunately, the design included some inadequacies.