Highly boron-doped diamond microelectrodes were fabricated by depositing the diamond crystallites on electrochemically etched tungsten wires using microwave plasma chemical vapor deposition and were sealed in glass with epoxy. The diamond tip was exposed by mechanical polishing. The resulting electrodes exhibited sigmoidal voltammetric curves at low potential sweep rates in aqueous electrolyte, consistent with microelectrode behavior. The Limiting currents were found to be independent of sweep rate up to values that were dependent on the electrode size. The high sensitivity of the diamond microelectrodes was demonstrated by the fact that a well-defined voltammogram was obtained for a solution containing 2 x 10(-7) M Fe(CN)(6)(4-). The diamond microelectrode behavior was found to be stable for several weeks, in contrast to that of unmodified carbon fiber microelectrodes.