Objective: To characterize oclussal relationships in primary and early mixed dentition and arch dimensions in sagittal, transversal and vertical planes. Materials and methods: This descriptive study considered a convenience sample of 107 children with an average age of 5.69 years (59 girls and 48 boys) registered in ten schools. Panoramic and cephalometric radiographs and study models were taken according to validated protocols. Panoramic radiographs showed the position and angulation of the first permanent molars. Results: 84% of patients in the study were characterized by having complete dentition, having a left and right molar relationships in flat terminal plane, an increased vertical overbite, an anterior superior width in a range between 27 and 32 mm, a superior posterior width between 32 and 39 mm, an anterior inferior width between 22 and 27 mm and an inferior posterior width between 39 and 46 mm. The inclination angle of the first superior molar is between 25 and 36 degrees. Conclusion: Most patients had arch dimensions and canine and molar relationships within the normal parameters as reported in the literature. Increased overbite and overjet in vertical and horizontal planes were found. In primary dentition, flat terminal plane and Class I canine relationship predominated. Only in 16 patients was applicable permanent molar relationship, of which 9 had class II.