Abstract: A releasable interlock assembly having axial and rotational engagement, and suitable for use in catheter introducers and other medical devices, has a tapered female member which receives a tapered male member. The female member has protrusions which engage corresponding grooves on the male member. The grooves have a generally axially aligned portion and a generally circumferentially aligned portion, terminating in a pocket to receive the corresponding protrusion on the female member. The depth of the each groove decreases from the open axially aligned end to a point just before the pocket, causing a dimensional interference which prevents the protrusion from disengaging the pocket axially, unless deliberately rotated by an operator.