Between 15th June 1991 and 15th August 1992, 40 patients underwent aortic valve replacement with the newly designed Edwards stentless aortic bioprosthesis 2500. The patients' ages ranged from 24 years to 80 years (mean 60.3 years). Preoperatively, 17 patients presented with pure aortic stenosis, three with aortic regurgitation and 20 with mixed lesion. The operations were performed with normothermic extracorporeal cardiopulmonary bypass and cold cardioplegic arrest. The implanted valves ranged in diameter from 21 mm to 27 mm. Ten patients received a subcoronary implantation, with the lower row of sutures being interrupted and the upper being continuous. The so-called miniroot technique was used in the other 30, also involving lower interrupted and running upper sutures after adaptation of the coronary ostia to the preformed openings in the graft. The aortic cross-clamp time ranged from 51 minutes to 94 minutes (mean 71 minutes). There was no operative mortality but three patients died early after the operation due to cardiac tamponade, sepsis and pneumonia. There was no late mortality or morbidity in the surviving patients up to 16 months postoperatively. Echocardiography, performed at discharge and twice a year thereafter showed no signs of significant valve incompetence in any patient, and continuous wave Doppler measurements indicated that resting pressure gradients across the aortic valve were low or absent. Our preliminary experience with the stentless aortic xenograft shows improved hemodynamic function as compared to stent mounted xenografts or mechanical prostheses. Further studies are needed, however, to establish the long-term performance of this device.