The deposition of nanocolloidal gold particles under the influence of an externally applied electric field is studied in situ by means of spectroscopic ellipsometry. Tile variation of the relative coverage with time, as a function of applied potential, is determined using a principal component analysis. Calibration of the absolute coverage is done by means of ex situ electron microscopy. The results reveal that the deposition rate is directly related to the electrochemical current. A threshold potential exists for current and therewith also deposition to occur. The spatial distribution of nanoparticles deposited in an applied field exhibits a higher degree of order as compared to the random, irreversibly deposited nanocolloids at chemically functionalized surfaces. The experimental findings are discussed in terms of a simple electrochemical model. (c) 2007 Elsevier B.V. All rights reserved.