The Medtronic Mosaic® valve is a new stented porcine bioprosthesis incorporating advanced concepts: a supra-annular stent, zero-pressure tissue fixation, and anti-calcification using 2-amino-oleic acid (AOA®). Between August 1994 and June 1997, 158 isolated aortic valve replacements were performed with this valve. Most patients (n = 152) were aged over 70 years; mean age was 73.7 years. All valves were implanted supraannularly. Thirty-two (20.2%) patients underwent concomitant procedures. Anticoagulation (heparin) was prescribed only in the immediate postoperative period; thereafter, none was prescribed except for patients in atrial fibrillation. Long-term follow up comprised clinical and echocardiographic studies. Twelve patients died (seven early (4.4%, 0-30 days) and five late (2.1%/pt-yr)). One death was valve-related. No thromboembolic complications or structural valve deterioration were observed during follow up. Two-year freedom from hemorrhage, endocarditis and reoperation were each 99.6%. At one year follow up, 98% of patients were in NYHA class I or II. The mean systolic gradients for the 21, 23, 25 and 27 mm valves at one year were 13.6, 13.2, 12.6 and 9.6 mmHg, respectively. This study will be continued to confirm the long-term benefits and durability of this new porcine bioprosthesis.