A child safety seat, for use in a vehicle, has a seat body (30), rear releasable connectors (34, 134) for rigid engagement with rear standard anchorage units on the vehicle, and front releasable connectors (36, 136) for rigid engagement with front standard anchorage units on the vehicle. The rear releasable connectors (134) are linked to the front releasable connectors (36, 136) by a coupling mechanism (52, 88, 92) which inhibits engagement of the front releasable connectors (36, 136) when the rear releasable connectors (134) are in their released position. The front releasable connectors (136) are mounted on retractable front legs (138) for movement between a deployed position and a stowed position, and blocking means (160) operate to inhibit engagement of the rear releasable connectors (134) when the front legs (138) are stowed.