A pulsatile pump of new concept has been developed for infant and pediatric cardiopulmonary bypass (cpb) (Parenzan-Fumero pump). A segment of elastic tubing is compressed by a pneumatically driven pushing plate under control of a microprocessor. Flow parameters such as pulse rate and stroke volume can be set. The pump can be synchronized with the patient's ECG for counterpulsation heart assist. A total of 87 open-heart procedures were performed using randomly either a conventional roller pump or the Parenzan-Fumero pump (respectively 39 and 48 patients). A previously published cpb protocol and anesthetic regimen were adopted in all cases. The results show increased cooling and rewarming rate (p less than 0.05) and urinary output, decreased vascular resistance, intensive care unit time and need for blood transfusion in the pulsatile group compared to the continuous perfusion group. In the pulsatile group, mortality was significantly lower (10.4% vs 25.6%) and low cardiac output syndrome was less frequent in the post-operative course.