The ability to control composition and size in the synthesis of bimetallic nanoparticles is important for the exploitation of the bimetallic catalytic properties. Such nanostructured catalysts could find important applications in fuel cell reactions. This presentation discusses recent findings of an investigation of a new approach to the synthesis of gold-platinum (AuPt) bimetallic nanoparticles of 2 –10 nm diameter in aqueous solution using a combination of reducing and capping agents. Mechanistically, the reduction of Au(III) was catalyzed by the formation of Pt as a result of the reduction of Pt(II). By controlling the precursor feed ratios, an effective route for the preparation of AuPt nanoparticles with a wide range of bimetallic compositions has been demonstrated. The composition, size and shell properties were characterized using transmission electron microscopy, direct current plasma-atomic emission spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electrochemical techniques. Implications of the results to the exploration of bifunctional catalysts in fuel cell reactions will also be briefly discussed