Abstract: A lockable key box having a tubular receiver portion with an integrally formed mounting flange, and a closure plug which is lockably receivable in an open end of the receiver portion. The closure plug is formed of an inner sleeve which fits within the outer sleeve formed by the receiver, and a master key-operated cylindrical lock mechanism which is retained within the inner sleeve so that a locking plunger extends from the lock mechanism through a transverse bore in the inner sleeve to engage a locking recess in the outer sleeve. The locking plunger is outwardly-biased and has a bevelled leading face so that the closure plug can be inserted into the receiver portion without using the master key. The receiver portion has a substantially continuous transverse cross section, so that it can be formed of extruded material, such as high strength extruded aluminum alloy.