A new technique for recording His bundle and right branch potential through the veins of the arm instead of by the femoral route is described. Recordings were carried out in 70 patients. In 10, His potential was recorded simultaneously by the femoral and brachial routes. Potentials proved to be similar as regards morphology and duration; A-V conduction time proved identical while there were slight variations in His node conduction time since the atriogram revealed varying intrinsic deflexions. It is thus possible to confirm that the recording of His potential by the brachial route offers various advantages: 1) it takes less time than the femoral route; 2) it is an excellent alternative if, for various reasons, the patient cannot be examined by the femoral route; 3) His potential can be monitored more easily because of the greater stability of the catheter and the provisional electrosimulation using the same catheter when necessary; 4) contemporaneous recording of right branch and His bundle potential is possible in association with the femoral technique with better results than those obtained using multipolar catheters; 5) it is without complications: i.e. the phlebitis, phlebothrombosis, a-v fistula, and pulmonary emboly which, however rarely, may occur when using the femoral route.