The accuracy and reliability of two-dimensional echocardiographic length method in right ventricular volume measurement were assessed by three-dimensional echocardiographic method in 10 normal children, 10 patients with atrial septal defect, and 10 patients with pulmonary stenosis. Their age and sex were matched. Right ventricular end diastolic, end systolic, mid-systolic volume, and ejection fraction evaluated by length method were correlated very well with the values obtained by three-dimensional echocardiographic method in normal and pulmonary stenosis group (r = 0.71-0.95, P < 0.01). In atrial septal defect group, right ventricular volume obtained by the two methods was correlated well (r = 0.86-0.95, P < 0.01). Although the correlation in right ventricular ejection fraction was lower, it was still significant. The shortening rate of X, Y, Z parameters required by length method were similar in each group: delta Z % > delta X % > delta Y %. We conclude that right ventricular volume and function could be assessed accurately by two-dimensional echocardiographic length method in children with right ventricular volume or pressor overloaded, and that right ventricular systolic pattern is similar in those situations.