BACKGROUND The effects of β-blockers on left ventricular (LV) remodeling have been established in patients with reduced ejection fraction (EF) after acute myocardial infarction (AMI). In AMI patients with preserved EF, additional effects of β-blockers on reperfusion therapy and current medical treatment have not been elucidated. METHODS Patients with preserved EF (≥40%), who underwent percutaneous coronary intervention (PCI) for AMI and obtained complete coronary revascularization were enrolled retrospectively. These were divided into groups treated with or without β-blockers at discharge. Echocardiography was performed on admission and 8months after PCI to observe LVEF, LV end diastolic volume index (LVEDVI), LV end systolic volume index (LVESVI), LV end diastolic diameter (LVDd), and LV end systolic diameter (LVDs). RESULTS A total of 114 patients were enrolled; 81 were treated with β-blockers (β-blocker group) and 33 were treated without β-blockers (non-β-blocker group). All patients were prescribed antiplatelets and 96% took either an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker. At follow-up, EF improved in both groups (2.6% in the β-blocker group and 4.6% in the non-β-blocker group). In the β-blocker group, neither LVEDVI nor LVESVI decreased. However, both LVEDVI (-4.3ml/m(2)) and LVESVI (-4.1ml/m(2)) improved in the non-β-blocker group. There were significant increases in LVDd (2.1mm) and LVDs (2.2mm) in the β-blocker group, whereas these parameters did not significantly change in the non-β-blocker group. CONCLUSIONS Effects of β-blockers on LV remodeling were uncertain in AMI patients with preserved EF, who obtained complete coronary revascularization and received optimal medical treatment.