An air-bag unit for a vehicle seat including a squab (2) and a back-rest (5). The back-rest (5) includes a frame which is covered with upholstery (7). An air-bag unit (22) has an inflatable air-bag (28) connected to an inflator (23) to inflate the air-bag 28. The air-bag unit 22 is mounted to the back-rest frame (6) so as to be located inboard of part of the frame (10) with the inflator (23) being located adjacent the rearmost region of the frame (6) and positioned to direct gas into the air-bag (28) in a generally forward direction. The arrangement is such that actuation of the air-bag unit (22) will cause the air-bag (28) to inflate so that at least part of the air-bag (28) lies between the frame (6) and the occupant (16) of the seat.