A new method for PID controller tuning based on process models for integrating and unstable processes with time delay is proposed in this paper. The proposed method is an extension of the PID controller tuning method by Lee, Lee, Park and Brosilow (1998) to general unstable and integrating processes with time delay. The proposed method is simpler to use because the proposed method is an explicit tuning method compared with other frequency response methods. Closed-loop responses tuned by the proposed method are compared with those of existing methods. The results show that the proposed tuning method gives better closed loop performance than the existing methods. (C) 2000 Elsevier Science Ltd. All rights reserved.