A rotating ring-disk electrode has been made by sputter depositing the disk and ring materials onto a quartz crystal substrate through masks. The design provides for separate electrical leads to ring and disk on the quartz surface. The collection efficiency determined experimentally with ferricyanide was not significantly affected by the presence of the leads. The new RRD electrode design permits the development of a a rotating ring-disk electrochemical quartz crystal microbalance electrode (RRD/EQCM) device for the simultaneous measurement of the disk current, the frequency shift of the quartz crystal and the ring current. The collection efficiency for oxygen was studied with gold disk and ring electrodes and was found to be significantly lower than that for ferricyanide. Using a titanium disk in combination with a gold ring, potential sweep experiments using the RRD/EQCM were carried out on the anodization of titanium in sulfuric acid. Above a potential of 3 V a mass loss was observed at the disk and oxygen was detected at the ring. (C) 2003 Elsevier B.V. All rights reserved.