It is natural that there is close relationship between cranial capacity, and the size of brain, several studies have estimated the cranial capacity which indirectly reflects the brain volume in different countries. In the present study cranial capacity has been estimated in Turkmans and native Fars17-20 years old groups in North of Iran.This study was carried out on 808 normal 17-20 years old (male 398, female 410) in Turkman and native Fars groups in South-East of Caspian Sea border (North of IRAN). By using linear dimensions of the head.The mean and SD of cranial capacity in Turkmans males and females were 1420.6±85 ml and 1227.2±120 ml, respectively. The mean and SD of cranial capacity in native Fars male and females were 1369±142ml, 1215.8±125ml, respectively, this difference was significant (P<0.05).This investigation was shown that the cranial capacity is higher in male than female, also racial factor can affect on cranial capacity.