Abstract: AIM: To investigate the clinical effect of cardiac resynchronization therapy for chronic heart failure patients with narrow QRS complexes. METHODS: Sixteen chronic heart failure patients with narrow QRS complexes received cardiac resynchronization therapy with left ventricle lead implanted into appropriate cardiac coronary vein. RESULTS: Cardiac function of 16 individuals was significantly improved after treatment. NYHA class of the patients improved from class III-IV to class II-III. After treatment, left ventricular ejection fraction (LVEF) significantly increased ［(0.31± 0.11)% vs.(0.38±0.10)%, P<0.05］ and the cardiac stroke volume (SV) also significantly increased ［(74±8) ml vs.(96±4) ml, P<0.05］. Mitral regurgitation (MR) significantly diminished (8±4)cm2 vs.(6±3)cm2, P<0.05］ and left ventricular end diastolic diameter (LVEDD) and left systolic diameter (LVESD) decreased (69±7)mm vs.(68±9)mm, (59±10)mm vs.(56±11)mm, P>0.05］. CONCUSION: These results suggest that cardiac resynchronization therapy is effective for some chronic heart failure patients with narrow QRS complexes.