Background and aim of the study-Early and mid-term clinical outcomes after aortic valve replacement (AVR) with stentless bioprostheses in a large cohort of patients are presented.Methods: Between April 1996 and November 2005, 1014 patients underwent aortic valve replacement with the stentless Medtronic Freestyle bioprosthesis, 168 as full-root technique.The mean age was 73±3 (range: 20-90) years.Follow-up included 2953 patient-years and was 95% complete for adverse events.Results: Operative mortality was 3.4% (N=34).Overall survival was 46±9% at 9 years and similar to age and gender matched German general population.Freedom from prosthetic valve endocarditis, major bleeding, neurological events and reoperation, after 9 years was 97±6%, 92±7%, 70±16% and 92±9%, respectively.Freedom from structural valve deterioration was 97±5% at 9 years.During the learning phase, mean transprosthetic gradients of 23.5±3.0 mmHg and 24.8±3.1 mmHg were observed for valve size 21 and 23 mm, respectively, ten days after subcoronary implantation in 1997, which could be lowered to 16±2.1 mmHg and 14.9±0.9 mmHg in 2005, respectively, with increasing experience of the surgeons.During the follow-up period, mean gradients dropped on average by 15 mmHg in patients presenting higher gradients at discharge.Conclusions: The Freestyle stentless bioprosthesis showed encouraging mid-term durability with low rates of valverelated morbidity and can be safely implanted without increased operative risk even during the learning phase.Special training of the surgeons is recommended to achieve optimal haemodynamic performance.