Methods to control the quality of stimulation electrodes for human patients are desirable. The results of a comparative electrochemical evaluation of three types of ultramicroelectrodes presently used for neural stimulation are discussed. The iridium electrodes examined were fabricated from iridium wire or by thin film technology. Electrochemical protocols based on single cyclic voltammetry are proposed for quality control. Defective insulator-conductor seals have been modelled and the simulation provides the basis for the protocol. The porous metal produced by thin film methodology is detected. The consequences of these defective structures for activation to hydrous iridium oxide coated electrodes for neural stimulation are discussed.