The maximal systolic velocity of the mitral annulus motion (or maximal systolic long-axis contraction velocity of the ventricle, MLACV) has been suggested as a means to assess left ventricular function. However, reference values for a wide range of age and body size are lacking. The maximal systolic velocity was studied with M-mode echocardiography using the apical four- and two-chamber views. Data are reported as the average of the measurements of four sites of the mitral annulus. Fifty-seven healthy subjects aged 6 months to 72 years were studied. In children and adolescents up to age 18, MLACV had a significant positive correlation with age, height, body surface area, weight and mitral annulus motion amplitude and a significant negative correlation with heart rate. In adults, there was a significant positive correlation between MLACV and height, mitral annulus motion amplitude and body surface area and a significant negative correlation with age and heart rate. Multiple stepwise analysis showed that the maximal systolic velocity is highly dependent on height and age in children and adolescents up to age 18, and on height in adults. The maximal long-axis contraction velocity (MLACV) can be described by the following equations: MLACV (mm s-1) = 24.0 + 0.34 x height (cm) (Standard Error of the Estimate (SEE)=10.5) in children and adolescents, and MLACV (mm s-1) = -50.5 + 0.75 x height (cm) (SEE=9.8) in adults over 18. There were significant differences between the four sites, with the highest velocity at the lateral site and the lowest velocity at the septal site. No significant difference was found between inspiratory and expiratory beats.