Abstract: A child resistant closure for a container having a threaded neck. The closure comprises a cap including a disc-shaped end wall and an internally threaded depending cylindrical side wall or skirt having an annular bottom end surface. A yieldable ledge or collar is on the neck of the container in a position to be engaged by the end surface of the cap side wall when the cap is threaded fully onto the neck of the container, and a shaped, interfitting lug and recess are on the collar and cap end surface in a position to be automatically interengaged everytime the cap is threaded fully onto the container to lock the cap in a fully closed position on the container. The collar is yieldable to enable selective release of the lug and recess to thereby enable retrograde movement of the cap from the threaded neck.