The angles of the seat pan and backrest of a chair can affect the pressure distribution. A method is needed to locate and quantify these pressures in the buttocks, thighs, and back in order to provide useful inputs for design. This paper describes an experimental chair which permits continuous measurements of pressure on both the seat pan and backrest. This chair refines and advances an optical reflection technique developed several years ago. The methodology allowed very precise quantitative measurements of sitting pressure to be recorded, which could be displayed either graphically, or be used in quantitative analyses.