The optimum shape and arrangement of staggered pins in the channel of a plate heat exchanger are studied in this paper. The following four dimensionless geometric parameters of the pins are selected as the important design variables: the distance (L), the volume (V), the angle (beta) and the pitch (G). The pressure drop and heat transfer characteristics are examined, and an optimization is carried out to minimize a global objective function consisting of the correlation between the Nusselt number and the friction factor. The optimal geometric parameters are as follows: L = 0.272, V = 0.106, beta = 0.44 and G = 0.195. The optimal geometric parameters obtained from this study can be applied for a Reynolds number ranging from 500 to 1500. (C) 2001 Elsevier Science Ltd. All rights reserved.