We encountered a rare complication of mitral valve replacement with the CarboMedics prosthesis: a "stuck" leaflet detected by transesophageal echocardiography even though weaning from cardiopulmonary bypass had been uneventful. The patient was immediately managed without significant problems. We emphasize the importance of performing routine intraoperative transesophageal echocardiography in valve replacement as well as in valve repair, from the initial phase of operation. (Ann Thorac Surg 1999;67:1484-5) (C) 1999 by The Society of Thoracic Surgeons.