The usual methods of recording the His bundle activity have been based on triggered signal averaging and commonly used analog filters. These filters are of low-frequency cutoff ranging from 10 to 80 Hz and high-frequency cutoff up to 300 Hz. The use of digital filters is studied in the external recording of the His bundle potential which also employs a cross-correlation function for the alignment of the waveforms. By using a low cutoff frequency of 30 Hz and a high-frequency cutoff of 250 Hz, the His bundle is found on the isoelectric line with amplitude between 4 to 7 μV. Fourier analysis of the His bundle waveform thus obtained shows that 90% of the power spectrum is below 150 Hz.