Abstract: A chair having a tiltable back which is vertically adjustable into selected vertical positions. The adjustment mechanism includes rack and gear members which are selectively engagable to lock the back in selected vertical positions. The rack member is secured to a support column and the gear member is secured to the back. The back height adjustment mechanism permits the back to tilt about a first axis and to pivot about a second axis, to release the rack and gear members for vertically repositioning the chair back. When the bottom edge of the chair back is pulled forward, the gear teeth of the cooperating rack and gear members are disconnected thereby enabling vertical movement of the chair back. Upon release of the bottom edge of the chair back, a bias spring urges the rack members together to hold the chair back in the selected vertical position.