Abstract: A chair seat support apparatus includes a base column internally housing means automatically operable only when the chair seat is unoccupied to allow vertical altering of the height of the seat upon rotation thereof. A screw post is journalled within the base column by means of vertically displaceable upper and lower bearings between which is disposed a notched adjustment nut carried by the screw post. Spring means, responsive to an unoccupied chair seat, urges the lower bearing upwardly which in turn vertically displaces the adjustment nut and its captive screw post. Stop means carried by the base column limits the vertical displacement of the adjustment nut and also precludes arcuate motion of the adjustment nut when elevated such that subsequent rotation of the chair seat and screw post produces vertical displacement thereof relative the base column and adjustment nut.