This study described our experience with the use of the timed Frank vectorcardiogram in 100 normal subjects and in 80 patients with various types of cardiac arrhythmias. It was shown that this techniques was of definite clinical value in recognition of cardiac arrhythmias. With this approach, high frequency, high speed records were readily available displaying the sequence of atrial and ventricular activation in a more precise way than the routine electrocardiograms. Records with a high degree of amplification were easily obtained which facilitated the identification of the time of inscription of the P loop and its relation to the QRS. It is concluded that this approach is of value in the study of cardiac arrhythmias and that it recorded in many situations information which was not readily available on the routine electrocardiogram.