This paper reports the etiology and the findings of phonocardiograms and echocardiograms in four cases with mitral regurgitation caused by the redundant chordae. Redundancy of the chordae were determined by the surgeon during operation. The results were as follows: 1. The etiology of redundant chordae was either congenital, rheumatic, or mucoid degeneration. 2. Phonocardiographic findings of this condition are a holosystolic murmur accompanied by a diastolic rumble at the apex. 3. Two-dimensional echocardiogram shows holosystolic bulging of the mitral leaflet to which redundant chordae are attached. 4. The findings of the M-mode echocardiogram are multiple linear echoes and bowing of the mitral valve in systole.