We investigated the effects of two new hollow-fiber membrane oxygenators, the Capiox SX10 and the Lilliput 901, on pulsatile versus nonpulsatile perfusion in an in vitro model designed to simulate a 3 kg infant. The experiments were divided into eight groups (six pulsatile and two nonpulsatile), according to the equipment and settings used. Each group included six tests. In all experiments, the pseudo-patient's mean arterial pressure was 40 mmHg, and the pump flow rate was 550 ml/min. During pulsatile cardiopulmonary bypass, the pump's base flow was set at 30%, and the pump rate was set at 80, 100, 120, 140, or 150 beats/min. The PUMP START and PUMP STOP timing points were adjusted to produce different pulse-width settings. We were especially interested in evaluating the pre- and postoxygenator extracorporeal circuit pressure (ECP), the oxygenator pressure drop, and the precannula ECP. When used with a pulsatile roller pump, the Capiox produced a significantly lower preoxygenator ECP than the Lilliput (p < 0.001); moreover, the Capiox yielded a significantly lower oxygenator pressure drop (p < 0.001). During nonpulsatile perfusion, the Capiox again produced a lower preoxygenator ECP than the Lilliput (p < 0.001). These results suggest that the Capiox may be more suitable than the Lilliput when the pulsatile flow is employed, and pulsatile flow does not increase the ECP with either oxygenator.