This reappraisal of the electrocardiographic manifestations of infarction of the lateral wall of the left ventricle is based on data acquired by simple and conventional technics. Categories of cases have been determined by the age of the infarct and the distribution of the lesion with respect to the circumference of the left ventricular wall and its epicardial and endocardial boundaries. Significant data have been presented in the form of illustrative diagrams and reproductions. The results do not establish a simple pattern common to all cases of infarction of the lateral wall; they do illustrate the varied yet limited electrocardiographic consequences of such lesions.