Background: Various heart diseases result in LV systolic dysfunction. We invested the distribution of cardiac disorders causing improvement of LV EF. Methods: 461 patients whose initial LV EF was ���50% and follow-up LV EF increased ���10% were enrolled. Heart diseases were arbitrarily divided into 7 categories in order of frequency: 1) ischemic heart disease(IHD); 2) tachycardia-induced cardiomyopathy(TCM); 3) dilated cardiomyopathy(DCM); 4) stress-induced cardiomyopathy(SCM); 5) hypertensive cardiomyopathy(HyCM); 6) valvular heart disease(VHD); and 7) other diseases. Results: Mean age was 63.3짹14.4 years. 267 patients (57.9%) were male. Mean initial LV EF was 34.0짹9.0%, follow-up EF was 51.9짹7.9%, and mean EF change was 17.9짹7.0%. Follow-up echo was performed 11.7짹11.8 (0.1~61) months after initial study. IHD and TCM were the 2 most frequent etiologies of LV EF improvement (29.1% and 24.3%) (table). Both of initial and follow-up LV EF were lowest in DCM (27.2짹6.9% and 46.9짹8.2%). Initial and follow-up LV EF were highest in VHD (37.4짹9.0%) and SCM (55.3짹6.1%), respectively. Conclusion: IHD and TCM were the 2 most frequent categories causing improvement of LV EF accounting for more than 50%.