An introducer assembly 10 provided with a sheath 16 formed of a plurality of elongate sections 22-26 which are coupled to one another along their longitudinal sides 28,30 by a dovetail coupling 32,34. The sheath sections 22,Â26 are slidable longitudinally relative to one another, enabling the sheath 16 to be retracted in stages. This reduces the amount of friction which must be overcome in the use of the sheath 16 and in particular during the deployment of a medical device carried within the sheath 16. 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.
