To investigate the relationship between maturation of the spheno-occipital synchondrosis (SOS) with cervical vertebrae (CVM), dental development of the canine (DI), chronologic age and intra-rater / inter-rater reliability using retrospective cone-beam computed tomography, seventy-seven subjects were randomly selected into six groups based on age and sex. Spearman correlation coefficients and tabulations between stages of maturation indices were evaluated. SOS maturation was significantly correlated with CVM and age (r > 0.8). A weaker significant correlation coefficient was found between SOS and DI (r > 0.6). All males with fused SOS were in CVM stage 4 or later, while all females were in at least CVM stage 3. No subjects with open SOS were in the post-pubertal growth spurt age group and no subjects with closed SOS were in the pre-pubertal growth spurt age group. SOS maturation showed substantial and significant inter-rater and intra-rater reliability (kappa > 0.7). / February 2015