Infection has been observed in artificial heart experimentation to be of early onset and generally within the first 2 postoperative weeks. The organisms most often detected in blood cultures were Pseudomonas aeruginosa, Enterobacter cloacae, E. coli and Enterococcus, all of which are intestinal species. Contamination is thus thought to be the most plausible cause of perioperative infection. Absolute sterility must be maintained in animal care areas and blood access to these animals is to be minimized. Although prompt selection of a proper antibiotic therapy is essential, the eradication of infection maintains a poor prognosis. The time course of fibrinogen levels is a reliable index to determine the onset of infection.