The generation of membership functions for fuzzy systems is a challenging problem. In this paper, we present a new scheme for optimizing Mamdani fuzzy controllers. We optimize the membership functions with an extended Kalman filter. We describe the algorithm and compare it with gradient descent optimization of fuzzy membership functions. The methods discussed in this paper are illustrated on a simple automotive cruise control problem. We demonstrate that the Kalman filter can be an effective tool for improving the performance of a fuzzy controller