The contact between two liquid immiscible phases, aqueous solution and an organic solvent, dichloroethane, has been established through a microchannel drilled in the polyimide plate by photoablation. The dimensions of the channel, more precisely, the ratio of the diameter of the hole to the length equal to the thickness of the plate, are very critical parameters; the liquid introduction sequence is also important. The behavior is erratic when the organic phase fills the channel; this occurs only for long channels and when the solvent is introduced first. The electrochemistry is always stable and reproducible in the principal cases: when water is introduced before the solvent for a long channel or when the length of the channel is equal or shorter than its diameter whatever the liquid introduced first. The localization of the interface as well as the diffusion pattern have been studied by voltammetry and chronoamperometry of ClO4- transfer. When the interface is situated on the organic side of the channel, this asymmetrical situation, depending on the transfer direction, causes the liquid|liquid interface to behave like a recessed or an inlaid electrode. © 2001 Elsevier Science B.V. All rights reserved.