Objective: Poor R wave progression in right precordial leads is a relatively common electrocardiogram (ECG) finding that indicates possible prior anterior myocardial infarction (MI); however, it is observed frequently in apparently normal individuals. In contrast, reversed R wave progression (RRWP) may be more specific to cardiac disorders; however, the significance of RRWP in daily clinical practice is unknown. The purpose of this study was to clarify the significance of RRWP in clinical practice.Materials and Methods: We analyzed consecutive ECGs obtained from 12,139 patients aged ≥20 years at Mito Kyodo General Hospital in Ibaraki between November 2009 and August 2012. Our setting is a secondary emergency hospital in the community, and the study participants were inpatients or patients who visited the general or emergency outpatient departments. RRWP was defined as RV2 < RV1, RV3 < RV2, or RV4 < RV3. Regarding ECGs considered to show RRWP, we confirmed the presence or absence of an abnormal Q wave and whether ultrasound cardiography, contrast-enhanced computed tomography, coronary angiography, and/or left ventriculography were performed to obtain detailed information.Results: RRWP was identified in 34 patients (0.3%). Among these patients, 29 (85%) had undergone cardiac evaluation. The final diagnosis was previous anterior MI in 12 patients (41%) and ischemic heart disease (IHD) without MI in 5 patients (17%). All 17 patients with IHD had left anterior descending (LAD) artery stenosis. The other patients were diagnosed with dilated (two patients, 7%) and hypertrophic (one patient, 3%) cardiomyopathy, left ventricular hypertrophy (one patient, 3%), or pulmonary embolism (one patient, 3%). Only seven patients (24%) were normal.Conclusions: RRWP is rare in daily clinical practice; however, it is a highly indicative marker for cardiac disease, particularly IHD with LAD artery stenosis.