Background and Objective. Corpus callosum (CC), the main white matter cable which connects two hemispheres of brain, is important in special procedures such as stereotaxic surgeries vary in size, in different populations. Determination of possible size differences in ethnical groups has special values. Patients and Methods. The size of the CC on midsagittal view was determined in 76 normal male subjects using MRI of brain hemispheres in northern Iran. The size of rostrum, body, splenium, length, and height of CC was measured for each subject. The width of the body of the corpus callosum (B), the anterior to posterior length (L) and the maximum height (H) of the corpus callosum, and ratios B/L and B/H were also calculated. Results. The longitudinal dimensions of the CC were 70.21 mm and 74.05 mm in native Fars and Turkmens, respectively (P<0.05). The heights were 25 mm and 25.75 mm in native Fars and Turkmen subjects, respectively. The width of CC in Turkmen people was significantly higher than native Fars people (P<0.05). The Evans index in Turkmen group (0.314) was significantly higher than in native Fars (0.3). The B/L and B/H ratios were nonsignificantly different between two groups. Conclusion. The CC parameters vary in different ethnical groups in northern Iran.