The study sought to examine the relationships between ramal height, autonomic nervous system activity, as measured by the heart rate variance in inter-beat intervals, and masticatory muscle activity gauged by duty factors in circumpubertal children aged 10-14 years at the CVM3 stage. While age, masseter and temporalis muscle duty factors, and ANS tone (pNN50 and LF/HF) served as independent variables, ramus height was treated as the dependent variable.