Worsening of left ventricular performance had been recognized after mitral valve replacement for mitral regurgitation. The effects of chordal preservation on ventricular performance after mitral valve replacement have been assessed. Twelve patients with mitral regurgitation were allocated to group A (undergoing mitral valve replacement with chordal preservation), or to group B (undergoing mitral valve replacement with chordal excision). Transoesophageal echocardiography was recorded simultaneously with radial artery and pulmonary capillary wedge pressures. Load was varied by withdrawal of blood from a venous line of cardiopulmonary bypass and/or nitroglycerine bolus. Ventricular performance was assessed by the slope of peak systolic pressure-end-systolic volume relation (Eps), and by the slope of the left ventricular stroke work-end-diastolic volume relationship. Eps significantly decreased immediately after mitral valve replacement (P < 0.02), with no difference among two groups. Eps gradually increased to preoperative levels 10 days after surgery. Pre-load recruitable stroke work also significantly decreased after mitral valve replacement (P = 0.01). The decrease was significantly larger in group B (P < 0.04). These data support the hypothesis that chordal preservation during mitral valve replacement has beneficial effects on left ventricular performance.