A second case of malfunction of a Harken disk valve due to undue disk wear is reported. Two and one-half years after aortic and mitral valvular replacement, the patient had paraprosthetic aortic insufficiency and physical findings suggesting intermittent dysfunction of his prosthetic mitral valve. Catheterization showed intermittent hemodynamic abnormalities; fluoroscopic and cineangiographic findings indicated intermittent mitral regurgitation secondary to undue mitral disk wear. At operation, the excised valve showed normal struts and sewing ring but severe disk wear. There was loss of disk substance and rim notching.