There is disclosed a closure for a container for fluent substances which may be harmful if ingested, especially by a child of tender years. The closure consists of two parts: one is secured to that portion of the container which defines the pouring opening and the other is manipulatable with respect to the first to open and close the opening. The parts have respective elements, at least one of which is helical, adapted to be engaged upon relative rotary movement to open the pouring opening but so arranged and constructed that the rotary movement must be accompanied by sustained digital squeezing force on two opposite sides of the movable part in order that rotary movement results also in axial movement. Such axial movement thereby disengages a bead and groove connection normally maintaining the two parts in fluid-tight relation. Re-engagement is obtained by simple axial thrust of the movable part on to the other. In one aspect the exterior configuration of the movable part is frustoconical to render it more difficult for a child to grasp and pull.