Abstract: The connector keying system has a first connector housing (4) with a mating surface and a second connector housing (2) with a mating surface. The second housing (2) is movable relative to the first housing (4). In this system a programming of the keying shall occur automatically as the connector housings (2, 4) are mated together. This achieved as follows: A keying means receiving recess (23) is provided on the mating surface of the first connector housing (4) proximate an end thereof. A keying means is provided in the recess (23). The keying means has a first (22) and a second keying member (24). The first keying member (22) is secured to the first connector housing (4) by first securing means (50, 52). The second keying member (24) is frictionally maintained in corporation with the first keying member (22). The second keying member (24) has second securing means which are provided to cooperate with the second connector housing when the connector housings (2, 4) are mated together.