Abstract: A vehicle seat assembly comprising a substantially horizontal seat structure and a normally upright backrest structure. The backrest structure is carried on support arms pivotally connected to the seat structure for swinging movement about a fixed pivot axis extending laterally of the latter. A four-bar linkage adjuster mechanism is interposed between the seat structure and the backrest structure. The four-bar linkage of the adjuster mechanism terminates in a movable abutment engageable by an abutting portion of the backrest structure. Under control of the linkage the abutment is movable in the path taken by the abutting portion of the backrest when the latter is swung rearwardly from its normal upright position to a predetermined rearwardly inclined position.A releasable brake means holds the four-bar linkage and thereby the abutment against movement to block rearward inclination of the backrest structure.