The paper concentrates on a tracking control problem of a class of unknown feedback linearizable nonlinear dynamical models realized with the aid of a discrete-time fuzzy controller. A new method to adapt the parameters of the fuzzy controller is proposed. Under some mild assumptions on the class of the nonlinear systems, it was shown that the adaptive fuzzy controller satisfies the uniform boundedness of the closed-loop signals under a condition of persistency of excitation. Some passivity properties of the fuzzy controller are shown.