Preparing conductive composite bipolar plates for fuel cells by compression molding or injection molding is a promising research direction. The very key point is how to meet the requirement of conductivity and mechanical properties. Conductive composites containing either one kind of the same size conductive fillers or two kinds of the different size conductive fillers were prepared and their conductivity and flexural strength were also investigated. The results show that the conductivity of composites containing one kind of the same size conductive fillers improves but the flexural strength of composites decreases with the increase of the filler size. The conductivity and flexural strength of composites containing two kinds of the different size conductive fillers are higher than that of composites containing only one kind of the large size conductive filler (> 90 mu m) in the appropriate proportion to the small size filler in the conductive fillers. However, the flexural strength of conductive composites containing two kinds of the different size conductive fillers is always lower than that of composites using only one kind of the small size conductive fillers (< mu 5 pm). (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.