Abstract: An adjustable seat having a seat cushion and a backrest which are both secured to an underframe. The seat further includes a hydrostatic system of incompressible fluid contained within a closed circuit. The hydrostatic system includes individual actuators which bear against the seat cushion or both the seat cushion and backrest to adjust the inclination thereof. A shutoff member is provided to alternately allow and prevent movement of fluid within the closed circuit to change and then maintain a desired inclination.