A car seat includes a vertically adjustable head rest and harness support apparatus that will properly locate the position of the harness relative to the child in response to the positioning of the head rest. The head rest is movable along a curved track to provide horizontal clearance with respect to the vehicle head rest when in a fully raised position. The harness belt is trapped in a length adjustment lock and follows a path that extends around a fixed guide bar at the top of the car seat frame then downwardly through a guide member that directs the belt through an opening in the seat back for engagement with the child. The guide member is supported on a harness control tube that engages a rack device to fix the position of the harness control tube when the position of the head rest is selected.