Replacement of the mitral valve with an aortic valve homograft has become feasible. Clinical and hemodynamic assessments of eight patients who received the new homograft were made from 3 to 6 months following surgery. Marked improvement was reported by six patients and mild to moderate improvement by two. At rest the homografts functioned well, creating a trivial diastolic gradient between the left atrium and left ventricle and being mildly insufficient in two cases. On exercise there was moderate mitral insufficiency. Anticoagulants were used for 3 months following surgery and then discontinued. In 60 subsequent patient-months no thromboembolism has been observed. The data are as yet inconclusive, but the homograft shows promise of being a reasonable alternative to the prostheses currently in use.