The design of mechanical circulatory support devices typically requires a priori knowledge of the hemodynamic requirements of their intended use. These requirements are difficult to determine because of limited clinical experience. This is especially true for the pediatric population, for whom there is a dearth of longitudinal data. This report aims to provide both engineers and physicians with benchmarks for determining the optimal flow requirements and settings for pediatric ventricular assist devices that are currently being developed. Criteria were developed on the basis of estimates derived from various sources. The potential patient population was estimated by using the prevalence of children on the heart transplant waiting list and those placed on extracorporeal membrane oxygenation. Cardiac outputs were determined for individual weights and body surface areas, using published values for healthy and sick pediatric patients. The recommended pump range was optimized to include the most patients, while considering the design constraints. This study identifies a significant population of patients who would benefit from a device providing 0.52 to 1.92 l/min.