A fully implantable, axial flow blood pump has been developed in Fu Wai Hospital aiming for clinical use. This ventricular assist device (VAD), which was developed after numerous CFD analyses for the flow characteristics of the pump, is 58.5-mm long, 30-mm wide (including DC motor), and weighs 240 g. The pump can deliver 5 L/min for pressures of 100 mm Hg over 8,000 rpm. In this study, short-term hemocompatibility effects of the axial left ventricular assist device (LVAD) (FW blood pump) were evaluated in four healthy sheep. The device was implanted into the left ventricular apex of beating hearts. The outflow graft of each device was anastomosed to the descending aorta. The hemolysis, which was evaluated in vivo by free hemoglobin value, was below 30 mg/dL. Evaluation of serum biochemical data showed that implantation of the FW blood pump in sheep with normal hearts did not impair end organ function. Gross and microscopic sections of kidney, liver, and lung revealed no evidence of microemboli. Performance of the pump in vivo was considered sufficient for a LVAD, although further design improvement is necessary in terms of hemolysis and antithrombosis to improve biocompatibility of the pump.