Aortic or Mitral Valve Replacement With the Biocor and Biocor Supra

Inclusion Criteria: * Requires aortic or mitral valve replacement (heart surgery such as bypass is allowed at the same time) * Legal age * Signed informed consent prior to surgery * Willing to complete all follow-up requirements Exclusion Criteria: * Pregnant or nursing women * Already have had a valve replaced other than that for the scheduled replacement * Needs another valve replaced * Cannot return for required follow-up visits * Have active endocarditis * Acute preoperative neurological event (such as a stroke) * Renal dialysis * History of substance abuse within one year or is a prison inmate * Participating in another study * Had the Biocor or Biocor Supra valve implanted but then the device was explanted * Life expectancy less than five years