Coulomb friction remains one of the major difficulties arising in control design for mechanical systems. Control of a translational pneumatic servoactuator is a typical example of such a problem. The aim of this paper is to demonstrate that sliding-mode control can be successfully used to compensate the friction of the piston in the cylinder, which is both viscous and Coulomb. A fourth-order nonlinear state-space model of a rodless pneumatic servoactuator will be developed with both numerical simulation and experimental validation. The comparison of sliding-mode control with classic PID control will be presented.