ABSTRACT. New fetal growth curves for Japanese have been made with the cooperation of 37 major medical centers throughout Japan by the sponsorship of the Ministry of Health. They are reliable in regard to the adequacy of the sample number, the accuracy of the data on gestational age and the proper processes of composing growth curves. Effect of sex and parity are significant on weight but not on length and head circumference growth curves. The light-for-dates infant is defined as below mean -1.5 SD by the statistic analysis of their morbidity. These new official fetal growth curves will solve current confusion of several fetal growth curves from different institutions in Japan.