The relative ease of acquisition and safety of two-dimensional echocardiography has established it as the mainstay for routine cardiac imaging. Translation of imaging data into useful quantitative information, however, requires fitting the ventricle to a specific geometric model. Because of its complex shape and anterior position, many attempts at right ventricular quantitation by two-dimensional echocardiography have been criticized as impractical and not reproducible. A simple method incorporating subcostal and apical imaging was introduced in 1984. This approach appeared to combine accuracy and practicability but was never validated in a clinical setting because of the difficulties of subcostal imaging in adults. This study assessed the feasibility and accuracy of this technique in the pediatric population. Results of volume comparison to values derived by magnetic resonance imaging were r = 0.96, standard error of the estimate (SEE) = 19.3 ml, and mean difference = 15 +/- 19.4 ml and r = 0.97, SEE = 12.3 ml, and bias = 5 +/- 11.8 ml for diastolic and systolic volumes, respectively. Comparison of estimates of ejection fraction with magnetic resonance imaging demonstrated r = 0.90, SEE = 5.9%, and bias = 3% +/- 5.7%. Interobserver and intraobserver variability was 9.9% and 8.2%, respectively, for systolic volumes and 11.5% and 8.9%, respectively, for diastolic volumes. Evaluation of right ventricular size and function by this approach is comparable to determinations by magnetic resonance imaging and may be clinically useful in the management of pediatric patients.