Abstract: An oleopneumatic adjustable and deadened support column for a chair having a first cylindrical body, a second cylindrical body, a command bar, a first slidable piston between the first and second body, an annular upper floating piston and an annular lower floating piston, and a valve contained within the second body. The first cylindrical body is connected to a base of a chair and is charged with compressed air. The second cylindrical body is coaxial and telescopically slidable within the first cylindrical body. The upper end of the second body is adapted to be connected to a seat of a chair. The command bar is a lever positioned under the chair seat. The first piston is annularly fixed around the second body and in sliding sealing engagement with the inner surface of the first body. The upper and lower pistons define upper and lower oil chambers between the first and second bodies. The valve is actuable by the command bar so as to control a flow of oil between the first and second oil chambers.