In Japan a nationwide survey of school children's physical growth has been carried out by the Ministry of Education every year since 1900 except the years of World War II. An attempt was made to elucidate the growth acceleration in height by making use of the statistical date of the above-mentioned survey. The maximum growth age (MGA) in height was taken as an indicator of the growth acceleration. The results were as follows:
1. MGA in height was found to be gradually going down since before the war. The growth acceleration in the prewar years was found to fit a straight line. In the postwar years, the growth acceleration of boys born in the 1950's proceeded along the regression line based on the prewar acceleration rate.
2. Lowering of MGA in height of boys and girls born after the war was found to fit Gompertz and logistic curves. The postwar growth acceleration with its point of reference at the end of the war was remarkable: MGA in height went down by 2.0 years for boys and 1.5 years for girls in 25 years. This period, however, should be regarded as a convalescent stage after the repression of growth due to the war.
3. If the postwar growth acceleration was to be taken as a part of the whole phenomenon in gradual progress since before the war, as it actually was, the rate of acceleration for boys was 0.2 year per 10 years.
4. In the case of girls, the growth acceleration in the prewar years was slower than that of boys, and the progress in the postwar years surpassed the regression line based on the prewar rate. The prewar slower rate for girls as compared to boys can be attributed to a situation peculiar to Japanese social background. In the prewar days, girls' place was lower than boys' in both social and home life and this fact may have affected repressively on the physical growth of girls.
5. The growth acceleration is likely to proceed for some time to come but a prediction on the phenomenon must wait for further investigation.
