Presents an approach for designing a nonlinear tracking controller based on the ideas developed in backstepping control design. For a class of nonlinear control systems which are not input-output feedback linearizable the authors show that the proposed controller will ideally achieve asymptotic tracking if the numerical estimation error of some desired signals can be avoided. The authors apply this approach to the ball and beam system and demonstrate the controller's performance by computer simulation. The simulation result shows that the proposed controller yields better steady state error than other approximate feedback linearization schemes.