In this paper, an improved relay-based monitoring procedure is presented to on-line identify the maximum closed loop log modulus, L-c,L-max, for multiloop control systems. The proposed method addresses two potential problems inherent in previous methods: (a) too many relay tests are required; (b) the monitoring information fails to be exploited to redesign the controller when there is incentive to do so. Simulation results demonstrate the successful applications of the proposed on-line monitoring procedure as well as its utility in the redesign of the controllers.