Abstract: A user adjustable lumbar support apparatus for inclusion in a seat back, comprising an essentially rigid back plate having front and rear surfaces and adapted to extend vertically within a seat back, a front plate having a front and back surface and having an orthotic lumbar support contour at its said front surface, the contour preferrably being generally concave side-to-side and convex top-to-bottom, and a multi-chambered fluid actuator including at least a pair of independently inflatable chambers arranged vertically one chamber above the other, together with elastic means supporting the actuator and the front plate in assembled relationship to the back plate with the chambers between said plates to accommodate relative motion between the plates as the chambers are inflated and deflated. The fluid actuator preferrably is a distendable chamber member containing separated enclosed fluid receiving chambers.