This prospective multicentre study assessed the midterm clinical and haemodynamic results of the Edwards Mira curved bileaflet prosthesis in aortic position. From June 1998 to October 2000, 117 patients, mean age 64 years (31-78 years) underwent aortic valve replacement with the Edwards Mira valve in three institutions. Clinical status, haemodynamic performance and valve related complications were assessed. Serial echocardiographic examinations were performed at discharge and at least two years follow-up. Operative mortality was 1.7% (n=2). Follow-up was 100% complete (594.1 patient-years). Actuarial survival at one, three and five years was 96.5+/-1.7%, 93.9+/-2.2% and 88.4+/-3.0%, respectively. Freedom from thrombosis was 99.1+/-0.9%, from embolic events: 96.2+/-1.9%, from bleeding events: 96.4+/-1.7%, and from non-structural dysfunction 97.2+/-1.6%. There was no structural dysfunction. The peak gradient at discharge was 22.13+/-8.1 mmHg down to 20.8+/-8 mmHg at 28 months. The mean gradient at discharge was 12.7+/-4.5 mmHg at discharge down to 10.8+/-4.2 mmHg at 28 months. The permeability index was 53.3+/-10% at 28 months. The Edwards Mira aortic valve showed excellent midterm haemodynamic performance, good midterm survival and low valve related complications rate. Long term follow-up remains to be assessed.