Age determination is an essential step in the identification of human bony remains. Foramen magnum is a valuable landmark in the base of the skull and is of significant interest to forensic medicine, anthropology and anatomy. The aim of the study was to determine the age (among different age groups) from the foramen magnum using three-dimensional computed tomography. The present study is performed on 120 Egyptians from different age groups (from 1 year up to 65 years). The length of the foramen magnum (LFM) and the width of the foramen magnum (WFM) were measured on the 3D CT models. Then, foramen magnum index (FMI) and foramen magnum area (FMA) were calculated. The different age groups (1 – 9, 10 – 19, 20 – 29, 30 -39, 40 – 49,50 – 59 and 60+ years) show the mean LFM was 26.90, 35.75, 34.66, 34.42, 33.88, 33.27 and 32.50 mm respectively. Mean WFM was 20.90, 25.67, 29.47, 28.75, 28.47, 27.53 and 28.0 mm respectively. Mean FMI was 1.29, 1.39, 1.18, 1.20, 1.20, 1.21 and 1.16 mm respectively. Mean FMA was 444.2, 721.7, 804.3, 783.0, 759.3, 720.8 and 718.1 mm respectively. These values reveal that there is a significant difference between the four studied parameters and different age groups. This study elucidated that LFM decrease and WFM increase with aging. Subsequently, FMI tends to decrease with age. There was a weak positive correlation between age and LFM, WFM and FMA and there was a negative correlation between age and FMI.