The electrochemical properties of Au and Pd monolayer-protected clusters (MPCs), prepared by dendrimer-templating and subsequent extraction, are described. Differential pulse voltammetry was used to estimate the size of the MPCs, and the results were compared to microscopic data and calculated values. Purification of the extracted Au and Pd nanoparticles was not required to obtain well-defined differential pulse voltammetry peaks arising from quantized double-layer charging. The calculated sizes of the nanoparticles were essentially identical to those determined from the electrochemical data. The capacitance of the particles was independent of the composition of core metal. Transmission electron microscopy data overestimated the size of the smallest Pd nanoparticles because of inadequate point-to-point resolution.