The paper considers the variable-structure output-feedback stabilization of nonlinear uncertain nonaffine systems when the state vector is not completely available and the use of observers is required. The strategy of introducing integrators in the input channel is exploited to enlarge the class of tractable control systems. A full-order observer is designed and the control problem is solved by forcing a sliding regime for the observer. Depending on the type of uncertainties, conditions are found under which convergence to the unique ideal solution of both the system and the observer, either exponentially or with a bounded error, is proven. (C) 2012 Elsevier Ltd. All rights reserved.