From March, 1969, through June 1976, 108 porcine aortic xenograft valves were used for mitral or aortic valve replacement in 95 patients. This experience provides one of the longest follow-ups available for evaluation of the porcine bioprosthesis. The first fifteen valves were locally mounted on Cutter stents and preserved in buffered formalin. Subsequent valves were prepared by the Edwards and Hancock Companies with glutaraldehyde preservation. Oral anticoagulation was routinely used for the first 6 weeks following surgery. Hospital mortality was unrelated to the valve type. All but four of the surviving patients with formalin preserved valves have required reoperation because of valve failure. There have been two valve failures in the patients who received gluteraldehyde valves, but there have been no embolic or thrombotic complications. Late cardiac catheterization has shown hemodynamic results equal to or better than prosthetic valves. The continuing long-term results indicate that the porcine xenograft is the valve of choice for cardiac valve replacement.