A stent graft has a tubular wall (1) defining a main lumen with at least one fenestration (15) in the wall. A tube (17) extends from the fenestration into the main lumen and is in fluid communication with the main lumen. An extension leg stent graft can be deployed from a branch vessel into the fenestration to seal into the tube. A flared guide (89) associated with the fenestration can be provided interiorly or exteriorly. There is also disclosed a bifurcated intraluminal prosthesis having a body (1), a first leg (7) and a second leg (17), the first leg extending from the body and the second leg extending into the body.