Mitral valve replacement in the presence of severe annular calcification and an infectious lesion may be complicated by atrioventricular rupture, left circumflex coronary artery injury, and recurrence of infective endocarditis. Confronted with these circumstances, we have developed a technique of annular reconstruction for mitral valve replacement. The prosthetic valve is made by enlarging the circumference of the sewing ring with a Dacron collar. The collar can be sutured to the left atrial wall above the mitral annulus. This technique has been employed in five patients: three had extensive annular calcification, and two had acute valve endocarditis with destruction of mitral annulus. In all cases, the circumferential or partial annular reconstruction permitted secure implantation of the prosthetic valve. The one postoperative death was related to hemodialysis due to chronic renal failure. There were no other fatalities during the postoperative course, and the valves functioned normally. Our results suggest that this technique can be performed in high operative risk patients when mitral valve replacement is impossible using conventional techniques.