The mass uncertainty resulting from taking passengers, loading freight, and being disturbed by external forces is the main reason why the performance of electromagnetic levitation systems deteriorate. Thus, this paper proposes a self-tuning controller for electromagnetic levitation systems with unknown mass variations. The self-tuning controller is an extended version of gain scheduling for the general case of unknown scheduling parameters. Experimental results show the benefits of the scheme in cases of unknown mass variation compared with a conventional control methodology. (C) 2000 Elsevier Science Ltd. All rights reserved.