Seventeen patients with femoral arteriovenous bovine shunts (FAVBS) were evaluated to delineate the cardiovascular consequences of the procedure. The resting cardiac index (CI), as estimated by echocardiography, was increased in 8 patients (47%). Twelve of the 17 patients (71%) had more than a 20% reduction in CI after 5 minutes of shunt occlusion. In 6 of these, the CI returned to normal from an abnormally high value. As a group, the decrease in CI was significant (P = 0.001). This was accomplished mainly by a significant decrease in stroke volume (P less than or equal to 0.004). Signs and symptoms of congestive heart failure developed in 10 of the 17 patients during the year following FAVBS. Because of the marginal cardiac reverse in patients with renal failure and the significant increase in cardiac index resulting from FAVBS, alternative forms of vascular access should be used whenever possible.