Alumina membranes, with mean pore diameters of 100 nm, have been used as templates to control the electrodeposition of palladium. Deposition occurs at the polarised water-organic interface, leading to the formation of nanoparticles. The particles are formed at the mouth of the alumina pores, the locus of their formation being dictated by the position of the organic-water interface. It is shown that the relative position of the liquid phases with respect to the alumina is controlled by the surface wetting properties of the liquids, rather than gravity. This in turn controls the interfacial position and hence the size of the particles deposited. The presence of the alumina membrane prevents agglomeration. Electrochemical and electron microscopy data are presented in support of this proposed deposition mechanism. © 2003 Elsevier Ltd. All rights reserved.