Background: The foramen magnum is a structure present at the base of skull. In MLCs, morphometry analysis of foramen magnum is important. In our study aim is to determine whether the foramen magnum and angular fronto nasal junction are useful in sex determination in western UP population using 3D reconstruction of Philips ingenuity core 128 slice computed tomography scan. Objective: (i) To estimate the foramen magnum among male and females to establish its role in sexual dimorphism using 3D computed tomography. (ii) To estimate anterior-posterior diameter, transverse diameter of foramen magnum and fronto nasal junction among male and female. (iii) This will help the forensic experts at time of emergency, and type of analysis in trauma. Methods and material: In this cross-sectional retrospective study 63 males and 87 females patient referring to the department of radio-diagnosis and imaging, Teerthanker mahaveer hospital and research center, Moradabad, UP west, India were evaluated. The required information about the transverse diameter, anterior-posterior diameter of foramen magnum, angle of fronto nasal junction were assesses by computed tomography brain scan. CHI-square and Pearson correlation was used for the comparision of diameter between both sexes. Results: Mean value of anterior-posterior diameter in male is significantly higher than in female, 32.636±6.43> 31.29±4.57 and transverse diameter is significantly higher in male than in female, 26.271±3.05>25.788±2.79. Anterior-posterior diameter is statistically significant at P<0.003 and transverse diameter is P>0.248. The mean value of fronto nasal junction angle is significantly higher in female than in male, 126.31±12.22>118.81±10.33. It is statistically significant at P<0.002. Conclusion: In our present study conclude from fact and result is sex determination from foramen magnum and fronto nasal junction in UP west population in male and female is significant and it should be useful for sex determination

Foramen magnum, Fronto nasal junction, computed tomography, sex determination, western UP population