Fore and aft adjuster mechanism is capable of serving as the load carrying seat belt anchorage means for a suspension seat having a large amount of vertical travel for isolating the occupant from shocks and vibrations and substantial horizontal travel for adjusting the position of the seat fore and aft to the position most comfortable to a particular occupant. The mechanism insures that the seat belt will remain of the same tautness and angular position relative to the occupant regardless of the amount of fore and aft or vertical movement of the seat. The adjuster mechanism is positioned intermediate the seat base and the vehicle floor and includes a pair of fore and aft guide rails on its sides anchored to the floor and a pair of sliding cross rails anchored to the seat base. Cooperating locking pins on the cross rails and holes in the guide rails provide fore and aft adjustment of the cross rails on the guide rails. The rear cross rail also carries a link on each side which is pivoted at its free outer end to the seat belt attachment point on the seat base. The link allows for unhampered normal vertical and fore and aft movement of the seat while transferring the loading of the seat and occupant to the guide rails and floor in a crash situation.