In Phase I, Ir foil substrates will be coated with Plasmalene a strongly adherent parylene based insulating film. Holes will then be drilled through the Plasmalene with an excimer laser. Electrochemical measurements and microscopy will be used to characterize the quality of the insulator/metal seal and the area and morphology of the hole and surrounding insulation. The Phase II program will apply the fabrication methods developed during Phase I to Ir wire electrodes and develop the protocol necessary for commercial production of the electrodes using the new fabrication methods. At the completion of Phase II, it should be possible to provide high quality Ir ultramicroelectrodes at competitive prices.