Dipole ranging is a method to determine the location, strength and orientation of the heart vector from body surface measurements. This technique was applied to electrocardiographic data recorded from forty-five normal subjects and from twenty patients suffering an acute myocardial infarction. Moments and locations during the QRST interval were determined by the potential integration formulae of Gabor and Nelson. Results in the normal population showed stability of both variables during cardiac recovery. In subjects with acute infarction, dipole loci were stable during much of the ST-segments of loci compatible with the anatomic positions of the lesions. Thus, dipole ranging methods can provide physiologically relevant information when applied to human electrocardiographic problems.