An introducer assembly provided with a sheath formed of a plurality of elongate sections which are coupled to one another along their longitudinal sides by a dovetail coupling. The sheath sections are slidable longitudinally relative to one another, enabling the sheath to be retracted in stages. This reduces the amount of friction which must be overcome in the use of the sheath and in particular during the deployment of a medical device carried within the sheath. The structure can also substantially increase the precision of deployment of the medical device, as well as decreasing the force required during the deployment operation.
