A catheter device having a shaft that extends from a proximal end to a distal end to carry on its distal end a self-expanding implant for intraluminal advance on a guidewire and delivery of the implant to an implant site by proximal withdrawal of a longitudinal sheath that lies radially outside the implant in the catheter, the catheter including a first shaft element to pull the sheath proximally and a second shaft element to push the implant distally to prevent the implant moving proximally with the sheath when the sheath is pulled proximally, wherein the sheath is freely rotatable with respect to the first shaft element during the said intraluminal advance and, during proximal movement, is caused to abut the first shaft element at an abutment position by a reduced inner diameter portion of the sheath proximal of the abutment position.
