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Background&Objective: 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 Turkman’s 17-20 years old group in North of Iran. Materials&Methods: This study was carried out on 401 normal 17-20 years old (male 198, female 203) in South-East of Caspian Sea border (North of IRAN). By using linear dimensions of the head (Using Lee- Pearsom's Formula). Results: The mean and SD of cranial capacity in males and females were 1420.6±85 ml and, 1227.2±120 ml, respectively, this difference was significant (P<0.05). Conclusion: This investigation was shown that the cranial capacity is higher in male than female also racial and Geographical factors can affect on cranial capacity.