A study was conducted to measure and compare the levels of hemolysis generated by an intravenous membrane oxygenation device referred to as the Intravenous Membrane Oxygenator (IMO) in previous literature. The device is comprised of several hundred hollow fiber membranes of approximately 40 cm in length that are woven in a fabric and wrapped around a centrally positioned balloon. The balloon, which is similar in shape and volume to an intra-aortic balloon, is rapidly inflated and deflated up to 300 bpm to augment gas exchange. To evaluate the hemolytic nature of this device, an in vitro test system was developed, consisting of two identical test loops, each incorporating a device test section of 1 inch in diameter, a heat exchanger, a Biomedicus pump head, a compliance bag, a venous reservoir bag, and Tygon tubing. Both loops were primed with 1.5 L of a bovine blood solution and run simultaneously at 37°C for 6 hours at 4 L/min. Hematocrit and plasma free hemoglobin concentration were measured every 30 minutes to monitor hemolysis within each loop. This methodology was used to compare the hemolysis of the device at maximal pulsation with that of the control loop with an empty test section, as well as with a pulsing balloon of the same volume without any fibers. The results suggest that the hemolytic nature of the pulsating intravenous oxygenator is consistent with that of an intra-aortic balloon, a clinically used device not associated with any complications due to hemolysis.