Recording of His bundle potentials by means of non invasive technique was first obtained in 1973. The Authors used a computerized, high resolution cardiograph to study 26 patients, 17 males and 9 females, mean age 57.15 +/- 21.79 years. H wave could be identified and therefore H-V interval could be calculated in 19 patients (73%). H wave identification is based on its morphological differentiation from other bioelectrical signals present in P-Q interval and on its repeated presence in all, or at least in the largest number of the six available leads. This technique, based on averaging process, is very useful in depistage of acute and chronic A-V conduction troubles.