A Pt-Re/Al2O3 reforming catalyst with different levels of chlorine content prior to reduction has been studied by various techniques such as combined STEM/EDX, TPR, H-2 chemisorption and model reactions in order to investigate the effect of the chlorine content on the bimetallic particle formation. TPR, H-2 chemisorption and model reactions show that chlorine inhibits the formation of bimetallic particles in the Pt-Re/Al2O3 catalyst. The effect of chlorine is, however, limited. Direct measurements by STEM/EDX analysis could not reveal any significant differences in alloy formation by varying the chlorine content from 0.6 to 1.5 wt.%. In comparison, the effect of adding water during reduction has a greater impact on the final state of the metal particles.