We assessed the thickness of the normal left ventricular wall according to gender by performing twodimensional echocardiography in children. While a few studies have evaluated left ventricular wall thicknesses in children using two-dimensional echocardiography, there is little information related to the influence of gender throughout childhood. We evaluated 251 patients (128 males and 123 females) with innocent murmurs but without congenital heart anomalies, or coronary artery lesions or arrhythmias, as determined by repeated echocardiographic, and electrocardiographic examinations. Intra-ventricular septal thicknesses at end-diastole and end-systole, and left ventricular posterior thicknesses at end-diastole and end-systole were determined in the parasternal short-axis view. Significant gender differences were observed in the thickness of all four measurements. There was a linear relationship between the thickness of the left ventricular wall and height. Height was the most appropriate and practical index for assessing the thickness of the wall of the left ventricle in children.