A simple method is proposed for the calculation of the set point weighting parameter in PI/PID controllers for unstable systems with a zero. Unstable second order systems with a positive or negative zero are considered. The method consists of equating for the set point weighting parameter (beta). Simulation results are given for the improved performance for the systems with a positive or a negative zero with obne stable and one unstable pole. The performance of the set point weighted controller using the value of beta by the simple method is compared with that obtained by minimizing the ISE value by numerical optimization method. (C) 2004 Elsevier Ltd. All rights reserved.