An introducer assembly (10) is provided with a sheath (12) and carrier element (20). The sheath (12) is oval in axial cross-section and has an oval internal wall (24). The carrier element (20) has an outer wall (22) which is oval and which has a shape corresponding to the shape of the internal wall (24) of the sheath (12). The non-round shapes of the sheath (12) carrier element (20) extend the whole length of the introducer (10). This structure ensures that the sheath (12) and carrier element (20) cannot rotate relative to one another during deployment of the assembly (10). Thus, any medical device carried on the introducer assembly (10) will not be subjected to any relative rotation of the sheath (12) and the carrier element (20). This ensures that the integrity of the medical device is retained. The structure also increases the torque strength of the assembly (10), as well as providing the ability for the introducer assembly (10) to self-orient within the lumen of a patient. This can be particularly advantageous in the deployment of medical devices or instruments which are rotationally dependent.
