A prosthetic stent graft (10) includes a trunk (12) with a vascular graft bifurcated into two flow channels (20). The flow channels have a first taper angle, decreasing area along its length between the bifurcation point and an outlet. A leg section (40) of the stent graft includes a tubular vascular graft. An inlet of the leg section has a deployed diameter at least about the same size or larger than a deployed diameter of the outlet of the flow channels. The leg section has its own taper angle, preferably less than or about equal to, and more preferably about equal to the taper angle of the flow channel. The deployed diameter of the leg section inlet is preferably about the same size or larger than the deployed diameter of the flow channels adjacent the bifurcation point of the trunk section, and the deployed diameter of flow channel outlets are preferably about the same size or smaller than the deployed diameter of the leg section at an equal distance from the leg section inlet as the outlet is from bifurcation point.
