Three of nine patients in whom the Edwards low-profile valve was placed in the mitral position have shown serious valve malfunction. Two of these expired despite emergency valve replacement. The third valve was replaced semielectively, with a good outcome. The valve malfunction has resulted from pannus formation on the uncovered metal struts, with severe limitation of motion and cocking of the valve disc. It is felt that careful serial evaluation of signs, symptoms, and valve cinefluorography is mandatory in patients with this valve. Should one or more of these parameters indicate valve malfunction, especially if serial observations indicate progressive worsening, valve replacement with another type of prosthesis should be very seriously considered. Serial cinefluorographic observation of the disc motion is indicated even in a setting of clinical well being.