Echocardiographic measurements of the interventricular septum (IVS) and left ventricular posterior wall (LVPW) thicknesses were performed and the IVS to LVPW thickness ratios (IVS/LVPW) were obtained in 613 normal subjects ranging from 4 to 18 years of age (318 boys and 295 girls) in the mass screening examination. Means±S. D. of IVS/LVPW were 1.02±0.10,1.00±0.09,and 1.01±0.09 for boys, girls and total subjects, respectively. We separated these groups according to body surface area (BSA) into 3 classes, i. e.<1.0m^2,1.0-1.5m^2,and ≥1.5m^2,and found no statistically significant differences between the sexes and classes.