Newborn's body dimensions such as brain weight and cranial capacity can be basis for all changes in anthropometric indices and later problems. This study is undertaken on 978 term-born normal and native newborns in Thaleghany Hospital, Arak, Iran. The measurements of the heads were done according classic cephalometry. The cranial capacity and brain weight of males and female statistically evaluated by using c²- and t test and significance was set up at p<0.05. Means and SD of the cranial capacity were 606.2± 26 and 440.82 ± 28 for males and females. Means and SD of the brain weight were 627.41±30 for males and 456.24±32 for females. The data showed that cranial capacity and brain weight of males were greater for males than that for females. This data in accompany with other studies proves that, the manner of distribution of cranial capacity and brain weight neither is depend on the age nor the ethnicity of correspondents in Iranian population. The differences in the data of this study with other studies in Iran confirm the effect of ethnicity and environmental condition on cranial capacity and brain weight of Iranian population.