Abstract: A container closure system includes a plurality of equally circumferentially distributed pins extending outwardly from the tubular neck of the container near the opening. A detachable cap consists of nested inner and outer cap members. The inner cap member is dimensioned to receive the container neck and includes a plurality of sidewall openings for receiving the pins. The outer cap member has a plurality of locking wedges disposed on its inner surface. The inner and outer cap members are assembled so as to permit mutual rotation. Thus, when the cap is emplaced over the open end of the container, the pins are received in the openings to thereby inhibit mutual rotation between the inner cap member and the container. Then, a twist of the outer cap member in a clockwise direction brings the ramp portion of each locking wedge into engagement with one of the pins, thereby drawing the cap and the tubular member together to effect a secure closure.