An electromechanically riven totally implantable total artificial heart (TAH) was developed recently at Baylor College of Medicine. This experimental prototype was proven to be reliable and effective, yet small enough to implant inside the chest cavity of an average human patient. This Tah system was assembled by selecting and combining the best, simplest and most reliable features available from NHLBI TAH contract programs. Commercially available components with already proven long-term performances were used for this system. Now this experimental prototype TAH is ready to move onto the next stage of development. Fabrication of a preproduction prototype TAH has to move from the laboratory to a commercial firm. American BioMed, Inc., Houston, Texas, will fabricate four TAHs during Phase I of this proposed program. In vitro characterization of these units will be studied and results compared with those of the unit fabricated at the laboratory at Baylor. Reproducibilities of their performance among these four units will be studied. After their performances are proven to be satisfactory, we will move to Phase II of this proposed program. Long-term in vivo validation and endurance studies will be the main aim of the Phase II program.