We investigated the reasons for discrepancies between two-dimensional echocardiography (2DE) and left ventriculography (LVG) in detecting interventricular septal asynergy in anterior or inferior myocardial infarction. Twenty-six patients with anterior infarctions due to proximal lesions of the left anterior descending artery and 20 patients with inferior infarctions due to proximal lesions of the right coronary artery were studied by 2DE and LVG. A 2DE long-axis view, a short-axis view at the papillary muscle level, an apical four-chamber view (AP-4CV), and right and left anterior oblique left ventriculograms (RAO-LVG and LAO-LVG) were recorded. The interventricular septum (IVS) on LAO 60 degree-LVG was divided into the basal and apical portions. 2DE and LVG were independently evaluated individually by the same readers, and the interventricular septal asynergy was classified as hypokinesis, akinesis and dyskinesis. Anterior infarction About 80% of the patients with akinesis of the apical third of the IVS in a long-axis view or of the apical half of the IVS in an AP-4CV were assessed as having akinesis of the entire septum by LAO-LVG. Inferior infarction Asynergy was echocardiographically detected in the posterior IVS in a short-axis view at the papillary muscle level. LAO-LVG showed asynergy in the apical third of the posterolateral segment (segment 7) in all cases and akinesis in the apical IVS in six of 20 patients (30%). In conclusion, the extent of asynergy of the IVS in anterior infarction is overestimated by LAO-LVG compared to 2DE, and asynergy of the apex assessed by LAO-LVG in inferior infarction will correspond to that of the inferior segment by 2DE. This discrepancy is attributed to the different planes between a long-axis view and an LVG projection. We conclude both LVG and 2DE are mandatory for estimating accurately the extent of asynergy in the infarcted IVS.