The invention relates to a balloon catheter in particular for expanding stents in fenestrations comprising a first inner balloon (4) a second outer balloon (5) the second balloon (5) completely enclosing the first balloon (4) separate supply lines in the catheter (2) to the first (4) and the second balloon (5) by which the balloons (4 5) can be subjected to pressure independently of one another and a central lumen (3) for a guide wire. According to the invention both balloons (4 5) have in the expanded state a diameter in the proximal portions (P) which is expanded in relation to the distal region (D). fig-2
