Abstract: A chair (1), in particular a dentist's chair, which has a seat (3) and a backrest (2) which are connected with each other by means of a hinge (6) consisting of two movable parts in the from of an inner ring (8) and an outer ring (7) disposed concentrically therewith. The inner ring (8) is secured to the seat (3), while the outer ring (7) is secured to the sear (3). The outer side of the inner ring (8) engages the inner side of the outer ring (7), a ball bearing (11, 12) being mounted between the inner ring (8) and the outer ring (7). The invention provides a dentist's chair where the armrest follows the movement of a user's back.