Abstract: A passenger seat structure for vehicles which comprises an underframe having at least one seat with a back fastened thereto. The underframe includes a substantially horizontal supporting member which has only that end thereof which is adjacent one side wall of the vehicle by a support connected to the floor of the vehicle. The horizontal supporting member which may be hairpin-shaped has its individual legs interconnected and has one end of a reinforcement connected to the bottom side of the supporting member while the other end of the reinforcement member is connected to the support which latter is connected to the vehicle floor.