Tissue Doppler imaging is a new ultrasound technology that derives measurements of contraction and relaxation velocities directly from the myocardium. However, data on myocardial velocities by using tissue Doppler imaging have not been established in normal children. In 48 normal children, myocardial velocities were measured using tissue Doppler imaging at three different sites (base, middle, and apex) in the left and right ventricles and the interventricular septum. In the left ventricular wall, the peak myocardial velocities during early diastole (peak E), during atrial contraction (peak A), and during systole (peak S) waves decreased gradually between the base and apical sites, whereas the ratio of E to A waves (peak E/A wave ratio) did not change among the 3 segments. Similar findings were obtained from the myocardial velocities in the right ventricle and the interventricular septum. A systolic and diastolic velocity gradient was also observed between the different ventricular walls. Significant correlations of the tissue Doppler parameters with age or heart rate were observed. In the left ventricle, the peak E wave demonstrated a stronger relation with age (r=0.77) than with heart rate (r=-0.65). The peak A wave did not change with age but correlated with heart rate. The peak E/A wave ratio showed a weaker relation with age (r=0.54) than with heart rate (r=0.62). The peak S wave was related to age (r=0.65) and to a lesser extent to heart rate (r= -0.51). Similar relationships of tissue Doppler parameters with age or heart rate were observed for the right ventricle and interventricular septum. The heterogeneous pattern and age- and heart-rate-related changes in normal myocardium demonstrated in this study must be taken into account when attempting to identify altered regional myocardial function with tissue Doppler echocardiography.