A tiltable chair including a housing, a back support pivotally attached to the housing about a first horizontal axis and a seat support pivotally attached to the back support about a second horizontal axis and moveably supported by a curved track formed on the housing. A leaf spring includes a first end supported by the housing and a second end biasing the back support and seat support in an upward direction. Preferably, a fulcrum member, which includes a support surface having a curvilinear contour, is moveably supported in the housing and engages a bottom surface of the spring intermediate the first and second ends of the spring. Preferably, a linkage mechanism including a first and second link is adapted to adjust the position of the fulcrum. In another preferred embodiment, a gear housing is removably disposed in said housing and coupled to the fulcrum. In one preferred embodiment, rearward and forward tilt limiters are provided. In various preferred embodiments, the chair further includes a backrest having a plurality of openings, and armrests that are vertically, laterally and pivotally adjustable. In a preferred embodiment, a kit for assembling a seating structure includes a tilt housing having a plurality of connector arrangements comprising at least a first and second connector arrangement, a first seating arrangement having a first mounting arrangement configured to be connected to the first connector arrangement, and a second seating arrangement having a second mounting arrangement configured to be connected to the second connector arrangement.