A series of Pt-Ge/gamma-Al2O3 reforming catalysts have been prepared and studied by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and chemisorption. The catalyst performance in the reforming of octane was found to be dependent on the way in which the catalyst had been prepared, selectivity to aromatics being highest when the catalyst had been prepared by a coimpregnation route. The majority of the platinum was in the form of very small particles which could not be seen by the microscope, whereas either all or the majority of the germanium was in the ionic state. PtGe, Pt3Ge2, and Pt3Ge particles were found, together with platinum, in the bimetallic catalysts. Particle aggregation and alloy formation was observed for all the catalysts after they had been used in octane reforming.