An introducer for use in the implantation and retrieval of a device in a patient includes a catheter (43) within which a stylet (14) is slidably carried, the stylet (14) being biased to a retracted position by a spring (35) and deployable by depression of an actuator (50). A locking device (40) locks the stylet (14) relative to the catheter (43) such that the locking device (40) must be disengaged prior to operation of the actuator (50). In the preferred embodiment, both the locking device (40) and the actuator (50) must be actuated by movement thereof in a direction substantially perpendicular to the direction of motion of the stylet (14). In an alternative embodiment, it is the catheter (43) which moves relative to the stylet (14).
