An extension of a backstepping method for the stabilization of nonlinear systems with respect to a set is presented. Robust control laws providing the system with input-to-output stability are proposed. Possibilities of non-strict Lyapunov functions' application are discussed. The differences between a conventional backstepping method and an approach proposed in Kolesnikov (Synergetic Control Theory. Energoatomizdat: Moscow, 1994; 344) are analyzed. Performance of the obtained solutions is demonstrated by computer simulation for pendulum with an actuator example. Copyright (C) 2008 John Wiley & Sons, Ltd.