We designed this study to compare long-term results of St. Jude Medical and CarboMedics mechanical heart valves in the aortic position. We retrospectively analyzed the results of 174 consecutive patients who received either a St. Jude (n=80) or a CarboMedics (n=94) mechanical aortic valve from March 1992 through October 2004.The follow-up rate was 97.7%. The mean follow-up duration for the St. Jude group was 79.3 ± 35.0 and for the CarboMedics group, 70.0 ± 34.3 months. The cumulative follow-up was 523.8 and 530.1 patient-years, respectively. The 30-day mortality rates for the St. Jude and CarboMedics patients were 1.3% and 3.2%, respectively. The actuarial survival rate for the St. Jude group at 138.0 ± 4.7 months was 75.9% ± 0.1% and for the CarboMedics group at 130.8 ± 4.8 months was 69.8% ± 0.1% (P=NS). There was no structural valve deterioration in either group. Freedom from thromboembolic events was 87.7% for the St. Jude group and 83.0% for the CarboMedics group (P=NS). Freedom from bleeding events for the St. Jude group was 93.6% and for the CarboMedics group, 89.7% (P=NS).The results obtained from this study indicate that standard St. Jude Medical and CarboMedics aortic valve prostheses offer similar excellent clinical performance. Definitive judgment must await trials that are extensive, randomized, and prospective.