A new method for external recording of the His bundle electrical activity is described. Four hundred standard ECG waveforms were recorded and digitized at 1.28 kHz (8 bit resolution) and averaged with the aid of a CDC 6600 computer to reduce the random noise. A cross correlation function, which operates in the frequency domain using the Fast Fourier Transform algorithm, was employed to extract fiducial synchronizing marks for the waveforms alignment (triggering). Waveforms were filtered with a digital bandpass filter (30 Hz and 250 Hz low and high cut off frequencies respectively). The activity of the His bundle which was thus obtained was present on an isoelectric line, with signal amplitude of 4 to 7 microV. A strong correlation (r = 0.95, n = 10) was found between the HV intervals and the HQ intervals obtained from intracardiac electrograms and the new technique. It was concluded that the new method is convenient, reliable and can be successfully applied for the management of patients with various problems in their cardiac conducting system.