A tilt mechanism for a chair includes rotary stop means defining a plurality of selectable tilted positions of the chair seat/back. In another aspect, an anti kick-back feature is provided based. The mechanism includes upper and lower housing parts and a cushioning spring that normally maintains the parts in a rest position with respect to one another while allowing the mechanism to tilt. A further aspect of the invention provides an improved spring tension control that allows the spring to be installed and removed in a fully relaxed condition so that no special tools are required.