The exploration of gold and gold-platinum nanoparticles for catalysis of methanol oxidation and oxygen reduction reactions is interesting because of the unique catalytic properties of gold at nanoscale sizes. Gold and gold-platinum nanoparticles of 2-5 nm sizes with organic monolayer encapsulation were prepared. The nanoparticles were assembled on different supporting materials and thermally treated at different temperatures. Using CO as a probe molecule, the surface composition of the nanoparticles was characterized using transmission FTIR. The surface composition was then correlated with the electrocatalytic activities observed for methanol oxidation and oxygen reduction reactions. Some initial insights into the understanding of the relationship between the catalytic activity and the bimetallic surface composition are revealed. Implications of the findings to the design of gold-based bimetallic nanoparticle catalysts for fuel cell applications are also discussed. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA, 8/22-26/2004).