In this paper, we present a new approach to sliding mode control for induction motors. The novelty is in the sliding variable formulation. Unlike previous approaches, where a linear combination of system states is used, our definition is nonlinear and dynamic and, when the system is in sliding mode, an adaptive reference signal is realized which can explicitly counteract mismatched parametric uncertainties. This method is robust to parameter variations and the stability analysis is simple. Full state measurements are needed for implementation. Load torque and rotor resistance can be unknown but bounded.