A flow visualization method was implemented in the study of the fluid flow characteristics of a swirl type left ventricular bypass pump. A systematic combination of pump spatial inlet orientations, pump valves, and pump body geometry were examined in order to determine pump flow characteristics. Both still and high speed motion photography were made of operating, transparent pumps in a mock circulatory loop with a blood analogue fluid. Regions of pump stasis, low velocity flows, and eddy formation were identified. In -redesigning the bypass pump, several changes were implemented that stemmed from these flow visualization studies. The final pump design incorporated an angled, tangential inlet duct with a tilting disc valve and a tilting disc valve in the outflow tract. A low profile, nonocclusive diaphragm was used with a nozzle shaped pump body to improve internal pump flow. These modifications should minimize areas of possible clot formation and fibrin deposition in the pump.