In this paper, an estimator schemefor the rotor speed and flux of an induction motor is proposed on the basis ofa fourthorder electrical model. It is assumed that only the stator currentsand voltages are measurable, and that the stator currents are bounded. Thereare a number of common terms in the motor dynamics, and this is utilized tofind a simple error model involving some auxiliary variables. Using this errormodel, the state estimation problem is converted into a parameter estimationproblem assuming that the rotor speed is constant. Some stability propertiesare given on the basis of Lyapunov analysis. In addition, the rotor resistance,which varies with the motor temperature, can also be estimated within the sameframework. The effectiveness of the proposed scheme is demonstrated throughcomputer simulations and experiments.