The one-pole peripheral AVR lead reflects the changes in the electromotive power of the heart in a frontal plane in a reverse (mirror) image. In 620 subjects with healthy hearts, with the aid of an extended ECG method; the variants of the auricle-ventricle complex in AVR lead in norm and the separate heart positions, were studied. The pathologically changed P-wave was established to be presented by its typical forms (P-mitrale, P-pulmonale), but in a mirror image in AVR lead. The positive auricle wave in AVR is an important sign for the presence of right-auricular ectopic rhythm. In 80 patients with left-ventricular loading, pathologically enlarged S deflection was found. In 232 patients with fight-ventricular loading (mitral stenosis, chronic pulmonary heart), the increase of the amplitude of the deflection R AVR and the change in the ratio R/Q aVR over 1, is a valuable information about the degree of the right-ventricular loading. Those changes closely correlate with the changes in the ventricular complex with the right thoracic leads and with the spirographic and X-ray examinations. the role of AVR lend in the differential diagnostic determination of the additional deflection r'R'aVR1 V1 in certain forms of disturbed intraventricular conductivity is emphasized. AVR lead reacts dynamically with the separate sites of myocardial necrosis, with the appearance of unusual forms of the ventricular complex in AVR (increased first R deflection AVR in posterior-inferior myocardial infarction, occurence of rSr' forms in AvR in posterior-basal infarction and wide split ventricular complexes in anterior (anteriorseptal)infarction, complicated with a bundle blockade. Myocardial ischemia (subpericardial and subendocardial) is represented in A V R in an image reverse to the left thoracic leads. A general conclusion is drawn that the separate interpretation of the changes in AVR lead is not reasonable. Its differential diagnostic value grows only with its synchronic analysis with the rest peripheral and especially precordial leads.