Abstract: A lockable container spout closure includes a dished, externally threaded main cap adapted for threaded insertion into an internally threaded spout. A secondary cap covers the main cap and is rotatably secured thereto. A key-operable lock is mounted in the secondary cap and includes a fixed cylinder disposed in a cavity defined by the main and secondary caps. A key-rotatable barrel is located centrally in the cylinder and has a cam fixed to an end thereof and operable in response to rotation of the barrel between lock and unlock positions to shift a lock member between a first position wherein it will clear a stop projecting from the main cap upon rotation of the secondary cap, and a second position wherein it will engage the stop to thereby effect rotation of the main cap upon rotation of the secondary cap.