Abstract: A vehicle seat belt buckle has a flat tongue part with latching edges, and a socket part with spaced parallel plates defining a socket within which the tongue can be received. A latch member slides at right angles to the plane of the tongue to engage the latch formations to retain the tongue within the socket, the movement being imparted by latch member portions received in grooves of a push botton slidably guided for manual movement in the direction of insertion of the tongue. A spring urged detent retains the push button and thus the latch member in the release positions and is itself released by a portion of an ejector device when this is moved inwardly in the socket on insertion of the tongue. In a modification a spring biassed ejector prevents return of the latch member to its latching position after release of the tongue.