Composition-activity relationships are important when developing synergistic properties in multimetallic nanoparticles in catalytic reactions. This paper reports findings regarding correlations between catalytic activities and bimetallic compositions of carbon electrode-supported AuAg nanoparticles in the electrocatalytic oxidation of glucose in alkaline solutions. Electrocatalytic activities were characterized using voltammetric and electrolytic techniques, and were also compared with those obtained with gold and silver nanoparticle catalysts under the same conditions. Results from cyclic voltammograms at bimetallic AumAg100-m, (m: at%) nanoparticle modified-electrodes in H2SO4 solutions suggested that synthesized Au82Ag18 and Au73Ag27 nanoparticles were composed by atomically mixed Ag and An atoms, and not composed of Ag and An metal domains, in other words, they were homogeneous. On the other hand, Au4oAg60 and Au17Ag83 nanoparticles were heterogeneous, composed of Ag and An metal domains. Homogeneously bimetallic AumAg100-m nanoparticles showed improvements in electrocatalytic activity for glucose, and heterogeneous bimetallic nanoparticles did not show any improvements. The electrolytic product was strongly dependant on the composition ratio of Ag, regardless of whether nanoparticles were homogeneous or heterogeneous. AumAg100-m(100 - m = ca. 30) nanoparticles showed synergistic catalytic activities with both characteristic properties of Au-nano and Ag-nano nanoparticles. (c) 2007 Elsevier B.V. All rights reserved.