The Hancock II bioprosthesis was used for heart valve replacement in 614 patients from 1982 to 1990. Aortic valve replacement (AVR) was performed in 376 patients, mitral valve replacement (MVR) in 195, and aortic and mitral valve replacement (DVR) in 43. The mean age was 62.7 years, and 78% of all patients were in New York Heart Association functional class III or IV before operation. Coronary artery bypass graft was necessary in 232 patients and replacement of ascending aorta in 55. There were 31 operative deaths (AVR, 4%; MVR, 6%; DVR, 9%). Follow-up was complete in 98.5% of the patients and extended from 12 to 103 months, with a mean of 49 months. At the last follow-up, 85% of the patients were in New York Heart Association class I or II. The actuarial survival at 8 years was 79% +/- 3% for AVR, 68% +/- 4% for MVR, and 65% +/- 10% for DVR. The freedom from stroke at 8 years was 93% +/- 2% for AVR, 83% +/- 5% for MVR, and 90% +/- 5% for DVR. At the end of 8 years 96% +/- 1% of all patients were free from endocarditis, 92% +/- 1% were free from primary tissue failure, and 89% +/- 3% were free from reoperation. The actuarial freedom from valve-related death at 8 years was 98% +/- 1% for AVR, 86% +/- 5% for MVR, and 91% +/- 6% for DVR. Hemodynamic assessment was obtained by Doppler echocardiography in all operative survivors and demonstrated satisfactorily effective valve orifices and transvalvular gradients. The clinical results obtained with the Hancock II bioprosthesis have been gratifying, particularly in the aortic position. This bioprosthesis is our biological valve of choice.