An endoluminal prosthesis includes two stent grafts with a flexible bridge extending between and connected to the stent grafts. The prosthesis can be part of a prosthesis assembly for treatment of branched vascular systems and can function as an interconnected leg extension prosthesis in combination with a main bifurcated prosthesis. In treating abdominal aortic aneurysms, the prosthesis can be deployed within both iliac arteries.