The present invention relates to an endoprosthesis for endovascular treatment of thoracic-abdominal aortic aneurysms or dissections, wherein the endoprosthesis has a proximal region, an intermediate region and a distal region, comprising five inner cylinders parallel to the longitudinal axis of the endoprosthesis, said inner cylinders, having elliptical apertures in the intermediate region. The present invention also relates to an endoprosthesis for endovascular treatment of abdominal aortic aneurysms or dissections which compromise the iliac arteries, wherein the endoprosthesis has a proximal region, an intermediate region and a distal region, comprising an inner cylinder parallel to the longitudinal axis of the endoprosthesis, said inner cylinder having an elliptical aperture in the intermediate region.