The aim of this study was to investigate the clinical and angiographic importance of left anterior hemiblock (LAHB) during acute inferior myocardial infarction (AIMI) by comparing patient groups with and without LAHB after AIMI. One hundred seventy-two patients (141 men and 31 women) between 28 and 84 years of age (mean 55 +/-10 years) with AIMI were included in the study. Patients were divided into 2 groups according to electrocardiogram (ECG) criteria: group I comprised 25 patients in whom ECG pattern characteristic of LAHB developed, group II comprised 147 patients without this pattern. According to the electrocardiogram, patients were placed in group I if the mean QRS axis was deviated to the left < 30 degrees in the frontal plane with the following pattern: increased S-wave voltage and decreased R-wave voltage in leads II, the appearance of a deep S-wave in lead II, and a terminal positive R-wave in lead aVR. Coronary angiography was performed within 2 weeks. A coronary stenosis was considered if the vessel diameter was narrowed by > 50%. The dominant coronary artery was classified as right or left or balanced. The left ventricular ejection fraction (LVEF) was calculated from left ventriculography. The mean age of the patients in group I was significantly higher (58 vs 54 years, p = 0.007), while the risk factors were similar in both groups. Left anterior descending (LAD) and multi-vessel coronary artery disease (CAD) were found to be significantly higher in group I compared with group 11 (80% vs 38%, p=0.0001; 84% vs 52%, p=0.001, respectively). The mean LVEF was found to be lower in group I (51% vs 56%, p=0.04). Peak creatine phosphokinase MB (CKMB) values were not different (216 vs 162 IU/L, p = 0.09). The frequency of left dominant or balanced coronary artery was determined to be higher in group I (44% vs 17%, p = 0.018). LAHB development during AIMI can be an indicator of LAD lesions, multivessel coronary artery disease, and impaired left ventricular systolic function.