Background: Craniofacial structure is influenced by the evolutionary process of populations, which produces variations depending on ethnicities and regions.Employing cephalometry, standards have been determined for Class I patients, by age ranges and sex, but the same definition is lacking for Class III.This paper aims to characterize a Colombian mestizo population aged 5 to 13 years using McNamara's analysis measures in lateral cephalometric radiographs and to compare them with Caucasian Class I and Class III patients. Materials and Methods:A total of 1626 lateral cephalometric radiographs of patients who have not received previous treatment (851 males and 775 females; aged 5 to 13 years) were analyzed.Results: Measurements increase with age, are lower in the female sex, and only SN-PM decreases with age.Vertical measures (ANS-Me, Na-Me, S-Go, SN-PM) and sagittal measures (Go-Gn, S-N) in mestizo people differ more from the Caucasian Class I and Class III population.Maxillomandibular differential in all ages displays significant differences when compared to the Class III group with the Colombian sample and Caucasian Class I. Conclusions:In most measurements, the sample of mestizos shows to be significantly different from Caucasians.Skeletal Class III malocclusion differs from all malocclusions from an early age in its maxillary and mandibular components.