A catheter (1) for transvascular deployment of a radially compressible medical device (16) has a tubular outer body (2) within which is slidably mounted an inner tubular sheath (3) which in turn houses a guide wire (4) which is axially movable through the sheath (3). The medical device (6) is mounted on the guide wire (4) and can be collapsed within the sheath (3) and body (2) for deployment. An outer distal end of the sheath (3) is provided with circumferentially spaced-apart axial slits (7) extending proximally from the distal end of the sheath (3) which sub-divide the distal end of the tubular side wall of the sheath (3) into a number of complementary tube sections (8) which are movable apart when the sheath (3) is pushed out of the distal end of the body (2) to engage or deploy the medical device (6).