The electrocatalytic oxidation of methanol was investigated on PtRu electrodes of different atomic compositions at several temperatures (from 25 to 110 degreesC). Very active catalyst nanoparticles supported on active carbon (Vulcan XC 72) were obtained using the colloidal synthesis developed by Bonnemann et al. [11], allowing easy variation of the atomic composition. These electrocatalysts were characterized by TEM, EDX and XRD; results indicate that they consist of platinum nanoparticles decorated by ruthenium. Methanol oxidation was studied as a function of composition, temperature and methanol concentration. Two effects were investigated: the effect of the working temperature and the effect of the atomic composition. It appeared that for lower methanol electrooxidation overvoltages, the best catalysts are ruthenium-rich, whereas at higher overvoltages the best one is the Pt + Ru (80:20)/C composition, irrespective of the working temperature, either in half-cell or in a single DMFC.