A stent graft and delivery device assembly comprises a dilator 3, a stent graft receiving portion distal of the dilator, an elongate seal-engaging sleeve portion 185 distal of the stent graft receiving portion, a stent graft 35 mounted on the stent graft receiving portion, a stent graft cover 100 mounted around the stent graft, the cover having a maximum outer diameter, and an introducer 40 disposed around the elongate seal-engaging sleeve portion. The introducer has a hollow body, a haemostatic device 33 and an introducer catheter 45 extending from the hollow body. The inner diameter D of the catheter is greater than the outer diameter Y of the seal-engaging sleeve portion 185. The seal-engaging sleeve portion has a maximum outer diameter Y less than the maximum outer diameter C of the cover 100. The introducer catheter is constructed to facilitate blood flow from upstream to downstream of an introduction zone, either by having a plurality of holes therein, or being held in place by an inflatable toroidal seal.
