Abstract: A common feedthrough for an implantable apparatus for stimulating living tissue, such as a pacemaker, which permits both unipolar and bipolar operation of the pacemaker, is established by a sleeve filled with insulating compound, through which first, second and third conductors proceed. The second conductor and the third conductor are electrically linked to each other at one end, and the third conductor is connected to the sleeve via a joining element. The first conductor is connected to a stimulating pole of the apparatus and to an output terminal at which stimulating pulses are supplied. The free end of the second conductor is connected to an indifferent pole of the apparatus, and the free end of the third conductor is connected to a reference pole of the apparatus. With the conductors connected in this manner, the apparatus can be operated in a unipolar mode. If operation in a bipolar mode is desired, the third conductor is cut outside of the housing.