1.1 ,This practice covers a protocol for the assessment of the hemolytic properties of continuous, intermittent, and pulsatile flow blood pumps used in circulatory assist, including extracorporeal, percutaneous, and implantable devices. An assessment is made based on the pump's effects on the erythrocytes over a certain period of time. Adopting current practices for this assessment, a 6-hour in vitro test is performed on a pump placed in a device-specific recirculating blood loop that mimics the pressure and flow conditions of the expected worst-case clinical use of the device. If the ultimate goal of the testing is to evaluate the blood damage potential of a pump for clinical use, it is suggested that paired testing between the subject blood pump and a legally marketed comparator device be conducted using the same blood pool in a matched blood test loop so that a relative hemolysis comparison can be made.