Many authors have studied the correlation of cranial base flexure and the degree of mandibular prognathism and classification of malocclusion. This indicates that the cranial base flexure may or may not have an effect on the degree of mandibular prognathism and classification of malocclusion. This study evaluates the correlation of the pretreatment cranial base angle and its component parts to other dental and skeletal cephalometric variables as well as treatment time. The sample consisted of 99 Angle Class II and Class I malocclusions treated in the mixed dentition with cervical headgear and incisor bite plane. Thirty of the patients required full appliance treatment. Treatment duration averaged 4.3 years (SD, 1.5 years). Only the starting cephalograms were used to acquire linear, proportional, and angular cranial base dimensions using Ba-S-N (total cranial base), Ba-S/FH (posterior cranial base), and SN/FH (anterior cranial base). Pearson product moment correlation coefficients were computed and used to assess the association of the following skeletal and dental variables: N-Pg/FH, MP/FH, Y-axis/FH, U1/L1, L1/MP, A-NPg mm, A-Perp, B-Perp, and treatment time with the cranial base measurements. Significance was determined only when the confidence level was P < .05. Although there was no significant correlation of BaSN or SN/FH with NPg, the angular BaS/FH, linear BaS mm, and proportional length of BaS %BaN were all statistically negatively correlated to the facial angle. This indicates that the posterior cranial base leg is the controlling factor in relating the cranial base to mandibular prognathism.