This paper considers a control system design for a rotor-magnetic bearing system that integrates a number of fault-tolerant control methods. A survey is undertaken of possible system failure modes which are classified according to whether they are internal or external to the magnetic bearing control system. Improved tolerance to specific external faults is achieved through multivariable controller design with H-infinity optimised disturbance rejection criteria. Tolerance to internal faults requires the integration of additional control sub-systems, including a fault detection algorithm and a supervisory algorithm to reconfigure control on occurrence of a fault. Experimental results obtained from a flexible rotor system are used to demonstrate the effectiveness of the control implementations. (C) 2003 Elsevier Ltd. All rights reserved.