The purposes of this study are to examine documented fetal skeletal remains of Japanese, to measure the basilar part of the occipital bone, and to develop diagnostic standards for estimating fetal age at death which can be applied to poorly preserved skeletons. The sample is composed of 272 Japanese individuals of the early to middle twentieth century, whose ages were recorded in months from gestations of 5 to 11 months. The measurement items used here are the length, breadth, and index of the basilar part. The regression equations of gestational age in months for one or two variables were calculated. The results indicated that it is possible to use the regression equations to estimate the age at death of fetuses directly from the basilar part measurements. Another indicator for estimating age at death from the basilar part is the ratio of the width to the length, which was here expressed as the index of the basilar part. The width exceeded the length at 7 months and the basilar part changed with age from an anteriorly posteriorly long shape to a bilaterally wide one. It is concluded that the basilar part is a good indicator for estimating the fetal age at death.