An experiment was carried out over two heating seasons to test the performance of an inferential control scheme (ICS), which was designed to optimise the control of boilers in multi-zone heating systems [Building Services Engineering Research and Technology 4 (2003) 245], in a real installation. This paper presents the development of the prototype controller, method and result of the experimental testing. The experimental results show that the ICS can significantly improve the long-term performance, i.e. energy efficiency and thermal comfort, of the multi-zone heating system compared with conventional control schemes. It also demonstrates that the ICS can be implemented in a microprocessor-based controller and be commissioned using short-term monitoring data, which makes it a practical control technique. (C) 2004 Elsevier B.V. All rights reserved.