The aim of the study was to compare the supra-annular and intra-annular implantation techniques by evaluating the differences in early haemodynamic outcome (gradients, effective orifice area, regurgitation). Since August 1991, 200 stentless Bravo model 300 valves have been implanted. Patients were divided into three groups of consecutive cases: group 1 (n = 50) represents exclusively intra-annular implantation; group 2 (n = 50) is a transitional period: and group 3 (n = 100) comprises only patients with supra-annular implantation. Significant differences were found (P<0.001) in low postoperative gradients (mean < or = 10 mmHg): 24% in group 1, 42% in group 2, and 95% in group 3. Comparing groups 1 and 3, gradients were lower and effective orifice area was augmented in all valve sizes in group 3. Trivial central regurgitation was present in groups 1-3 (6%, 12% and 0% respectively). Peripheral regurgitation was trivial in 6%, 8% and 0% and mild to moderate in 4%, 2% and 0% (P<0.001).